diff --git a/ext/json/ext/parser/extconf.rb b/ext/json/ext/parser/extconf.rb
index f7360d46..e9a9f2f3 100644
--- a/ext/json/ext/parser/extconf.rb
+++ b/ext/json/ext/parser/extconf.rb
@@ -3,4 +3,29 @@
 
 have_func("rb_enc_raise", "ruby.h")
 
+# checking if String#-@ (str_uminus) dedupes... '
+begin
+  a = -(%w(t e s t).join)
+  b = -(%w(t e s t).join)
+  if a.equal?(b)
+    $CFLAGS << ' -DSTR_UMINUS_DEDUPE=1 '
+  else
+    $CFLAGS << ' -DSTR_UMINUS_DEDUPE=0 '
+  end
+rescue NoMethodError
+  $CFLAGS << ' -DSTR_UMINUS_DEDUPE=0 '
+end
+
+# checking if String#-@ (str_uminus) directly interns frozen strings... '
+begin
+  s = rand.to_s.freeze
+  if (-s).equal?(s)
+    $CFLAGS << ' -DSTR_UMINUS_DEDUPE_FROZEN=1 '
+  else
+    $CFLAGS << ' -DSTR_UMINUS_DEDUPE_FROZEN=0 '
+  end
+rescue NoMethodError
+  $CFLAGS << ' -DSTR_UMINUS_DEDUPE_FROZEN=0 '
+end
+
 create_makefile 'json/ext/parser'
diff --git a/ext/json/ext/parser/parser.c b/ext/json/ext/parser/parser.c
index 6f0e4ace..aaef53aa 100644
--- a/ext/json/ext/parser/parser.c
+++ b/ext/json/ext/parser/parser.c
@@ -97,7 +97,7 @@ static ID i_json_creatable_p, i_json_create, i_create_id, i_create_additions,
           i_chr, i_max_nesting, i_allow_nan, i_symbolize_names,
           i_object_class, i_array_class, i_decimal_class, i_key_p,
           i_deep_const_get, i_match, i_match_string, i_aset, i_aref,
-          i_leftshift, i_new, i_BigDecimal;
+          i_leftshift, i_new, i_BigDecimal, i_freeze, i_uminus;
 
 
 #line 126 "parser.rl"
@@ -869,6 +869,10 @@ case 28:
 
 #line 292 "parser.rl"
 
+    if (json->freeze) {
+        OBJ_FREEZE(*result);
+    }
+
     if (cs >= JSON_value_first_final) {
         return p;
     } else {
@@ -877,7 +881,7 @@ case 28:
 }
 
 
-#line 881 "parser.c"
+#line 885 "parser.c"
 enum {JSON_integer_start = 1};
 enum {JSON_integer_first_final = 3};
 enum {JSON_integer_error = 0};
@@ -885,7 +889,7 @@ enum {JSON_integer_error = 0};
 enum {JSON_integer_en_main = 1};
 
 
-#line 308 "parser.rl"
+#line 312 "parser.rl"
 
 
 static char *JSON_parse_integer(JSON_Parser *json, char *p, char *pe, VALUE *result)
@@ -893,15 +897,15 @@ static char *JSON_parse_integer(JSON_Parser *json, char *p, char *pe, VALUE *res
     int cs = EVIL;
 
 
-#line 897 "parser.c"
+#line 901 "parser.c"
 	{
 	cs = JSON_integer_start;
 	}
 
-#line 315 "parser.rl"
+#line 319 "parser.rl"
     json->memo = p;
 
-#line 905 "parser.c"
+#line 909 "parser.c"
 	{
 	if ( p == pe )
 		goto _test_eof;
@@ -935,14 +939,14 @@ case 3:
 		goto st0;
 	goto tr4;
 tr4:
-#line 305 "parser.rl"
+#line 309 "parser.rl"
 	{ p--; {p++; cs = 4; goto _out;} }
 	goto st4;
 st4:
 	if ( ++p == pe )
 		goto _test_eof4;
 case 4:
-#line 946 "parser.c"
+#line 950 "parser.c"
 	goto st0;
 st5:
 	if ( ++p == pe )
@@ -961,7 +965,7 @@ case 5:
 	_out: {}
 	}
 
-#line 317 "parser.rl"
+#line 321 "parser.rl"
 
     if (cs >= JSON_integer_first_final) {
         long len = p - json->memo;
@@ -976,7 +980,7 @@ case 5:
 }
 
 
-#line 980 "parser.c"
+#line 984 "parser.c"
 enum {JSON_float_start = 1};
 enum {JSON_float_first_final = 8};
 enum {JSON_float_error = 0};
@@ -984,7 +988,7 @@ enum {JSON_float_error = 0};
 enum {JSON_float_en_main = 1};
 
 
-#line 342 "parser.rl"
+#line 346 "parser.rl"
 
 
 static int is_bigdecimal_class(VALUE obj)
@@ -1005,15 +1009,15 @@ static char *JSON_parse_float(JSON_Parser *json, char *p, char *pe, VALUE *resul
     int cs = EVIL;
 
 
-#line 1009 "parser.c"
+#line 1013 "parser.c"
 	{
 	cs = JSON_float_start;
 	}
 
-#line 362 "parser.rl"
+#line 366 "parser.rl"
     json->memo = p;
 
-#line 1017 "parser.c"
+#line 1021 "parser.c"
 	{
 	if ( p == pe )
 		goto _test_eof;
@@ -1071,14 +1075,14 @@ case 8:
 		goto st0;
 	goto tr9;
 tr9:
-#line 336 "parser.rl"
+#line 340 "parser.rl"
 	{ p--; {p++; cs = 9; goto _out;} }
 	goto st9;
 st9:
 	if ( ++p == pe )
 		goto _test_eof9;
 case 9:
-#line 1082 "parser.c"
+#line 1086 "parser.c"
 	goto st0;
 st5:
 	if ( ++p == pe )
@@ -1139,7 +1143,7 @@ case 7:
 	_out: {}
 	}
 
-#line 364 "parser.rl"
+#line 368 "parser.rl"
 
     if (cs >= JSON_float_first_final) {
         long len = p - json->memo;
@@ -1165,7 +1169,7 @@ case 7:
 
 
 
-#line 1169 "parser.c"
+#line 1173 "parser.c"
 enum {JSON_array_start = 1};
 enum {JSON_array_first_final = 17};
 enum {JSON_array_error = 0};
@@ -1173,7 +1177,7 @@ enum {JSON_array_error = 0};
 enum {JSON_array_en_main = 1};
 
 
-#line 417 "parser.rl"
+#line 421 "parser.rl"
 
 
 static char *JSON_parse_array(JSON_Parser *json, char *p, char *pe, VALUE *result, int current_nesting)
@@ -1187,14 +1191,14 @@ static char *JSON_parse_array(JSON_Parser *json, char *p, char *pe, VALUE *resul
     *result = NIL_P(array_class) ? rb_ary_new() : rb_class_new_instance(0, 0, array_class);
 
 
-#line 1191 "parser.c"
+#line 1195 "parser.c"
 	{
 	cs = JSON_array_start;
 	}
 
-#line 430 "parser.rl"
+#line 434 "parser.rl"
 
-#line 1198 "parser.c"
+#line 1202 "parser.c"
 	{
 	if ( p == pe )
 		goto _test_eof;
@@ -1233,7 +1237,7 @@ case 2:
 		goto st2;
 	goto st0;
 tr2:
-#line 394 "parser.rl"
+#line 398 "parser.rl"
 	{
         VALUE v = Qnil;
         char *np = JSON_parse_value(json, p, pe, &v, current_nesting);
@@ -1253,7 +1257,7 @@ case 2:
 	if ( ++p == pe )
 		goto _test_eof3;
 case 3:
-#line 1257 "parser.c"
+#line 1261 "parser.c"
 	switch( (*p) ) {
 		case 13: goto st3;
 		case 32: goto st3;
@@ -1353,14 +1357,14 @@ case 12:
 		goto st3;
 	goto st12;
 tr4:
-#line 409 "parser.rl"
+#line 413 "parser.rl"
 	{ p--; {p++; cs = 17; goto _out;} }
 	goto st17;
 st17:
 	if ( ++p == pe )
 		goto _test_eof17;
 case 17:
-#line 1364 "parser.c"
+#line 1368 "parser.c"
 	goto st0;
 st13:
 	if ( ++p == pe )
@@ -1416,7 +1420,7 @@ case 16:
 	_out: {}
 	}
 
-#line 431 "parser.rl"
+#line 435 "parser.rl"
 
     if(cs >= JSON_array_first_final) {
         return p + 1;
@@ -1505,7 +1509,7 @@ static VALUE json_string_unescape(VALUE result, char *string, char *stringEnd)
 }
 
 
-#line 1509 "parser.c"
+#line 1513 "parser.c"
 enum {JSON_string_start = 1};
 enum {JSON_string_first_final = 8};
 enum {JSON_string_error = 0};
@@ -1513,7 +1517,7 @@ enum {JSON_string_error = 0};
 enum {JSON_string_en_main = 1};
 
 
-#line 538 "parser.rl"
+#line 542 "parser.rl"
 
 
 static int
@@ -1535,15 +1539,15 @@ static char *JSON_parse_string(JSON_Parser *json, char *p, char *pe, VALUE *resu
 
     *result = rb_str_buf_new(0);
 
-#line 1539 "parser.c"
+#line 1543 "parser.c"
 	{
 	cs = JSON_string_start;
 	}
 
-#line 559 "parser.rl"
+#line 563 "parser.rl"
     json->memo = p;
 
-#line 1547 "parser.c"
+#line 1551 "parser.c"
 	{
 	if ( p == pe )
 		goto _test_eof;
@@ -1568,7 +1572,7 @@ case 2:
 		goto st0;
 	goto st2;
 tr2:
-#line 524 "parser.rl"
+#line 528 "parser.rl"
 	{
         *result = json_string_unescape(*result, json->memo + 1, p);
         if (NIL_P(*result)) {
@@ -1579,14 +1583,14 @@ case 2:
             {p = (( p + 1))-1;}
         }
     }
-#line 535 "parser.rl"
+#line 539 "parser.rl"
 	{ p--; {p++; cs = 8; goto _out;} }
 	goto st8;
 st8:
 	if ( ++p == pe )
 		goto _test_eof8;
 case 8:
-#line 1590 "parser.c"
+#line 1594 "parser.c"
 	goto st0;
 st3:
 	if ( ++p == pe )
@@ -1662,7 +1666,7 @@ case 7:
 	_out: {}
 	}
 
-#line 561 "parser.rl"
+#line 565 "parser.rl"
 
     if (json->create_additions && RTEST(match_string = json->match_string)) {
           VALUE klass;
@@ -1678,7 +1682,22 @@ case 7:
     if (json->symbolize_names && json->parsing_name) {
       *result = rb_str_intern(*result);
     } else if (RB_TYPE_P(*result, T_STRING)) {
+# if STR_UMINUS_DEDUPE_FROZEN
+      if (json->freeze) {
+        // Starting from MRI 2.8 it is preferable to freeze the string
+        // before deduplication so that it can be interned directly
+        // otherwise it would be duplicated first which is wasteful.
+        *result = rb_funcall(rb_str_freeze(*result), i_uminus, 0);
+      }
+# elif STR_UMINUS_DEDUPE
+      if (json->freeze) {
+        // MRI 2.5 and older do not deduplicate strings that are already
+        // frozen.
+        *result = rb_funcall(*result, i_uminus, 0);
+      }
+# else
       rb_str_resize(*result, RSTRING_LEN(*result));
+# endif
     }
     if (cs >= JSON_string_first_final) {
         return p + 1;
@@ -1786,6 +1805,12 @@ static VALUE cParser_initialize(int argc, VALUE *argv, VALUE self)
             } else {
                 json->symbolize_names = 0;
             }
+            tmp = ID2SYM(i_freeze);
+            if (option_given_p(opts, tmp)) {
+                json->freeze = RTEST(rb_hash_aref(opts, tmp)) ? 1 : 0;
+            } else {
+                json->freeze = 0;
+            }
             tmp = ID2SYM(i_create_additions);
             if (option_given_p(opts, tmp)) {
                 json->create_additions = RTEST(rb_hash_aref(opts, tmp));
@@ -1849,7 +1874,7 @@ static VALUE cParser_initialize(int argc, VALUE *argv, VALUE self)
 }
 
 
-#line 1853 "parser.c"
+#line 1878 "parser.c"
 enum {JSON_start = 1};
 enum {JSON_first_final = 10};
 enum {JSON_error = 0};
@@ -1857,7 +1882,7 @@ enum {JSON_error = 0};
 enum {JSON_en_main = 1};
 
 
-#line 761 "parser.rl"
+#line 786 "parser.rl"
 
 
 /*
@@ -1874,16 +1899,16 @@ static VALUE cParser_parse(VALUE self)
   GET_PARSER;
 
 
-#line 1878 "parser.c"
+#line 1903 "parser.c"
 	{
 	cs = JSON_start;
 	}
 
-#line 777 "parser.rl"
+#line 802 "parser.rl"
   p = json->source;
   pe = p + json->len;
 
-#line 1887 "parser.c"
+#line 1912 "parser.c"
 	{
 	if ( p == pe )
 		goto _test_eof;
@@ -1917,7 +1942,7 @@ case 1:
 cs = 0;
 	goto _out;
 tr2:
-#line 753 "parser.rl"
+#line 778 "parser.rl"
 	{
         char *np = JSON_parse_value(json, p, pe, &result, 0);
         if (np == NULL) { p--; {p++; cs = 10; goto _out;} } else {p = (( np))-1;}
@@ -1927,7 +1952,7 @@ cs = 0;
 	if ( ++p == pe )
 		goto _test_eof10;
 case 10:
-#line 1931 "parser.c"
+#line 1956 "parser.c"
 	switch( (*p) ) {
 		case 13: goto st10;
 		case 32: goto st10;
@@ -2016,7 +2041,7 @@ case 9:
 	_out: {}
 	}
 
-#line 780 "parser.rl"
+#line 805 "parser.rl"
 
   if (cs >= JSON_first_final && p == pe) {
     return result;
@@ -2126,6 +2151,8 @@ void Init_parser(void)
     i_leftshift = rb_intern("<<");
     i_new = rb_intern("new");
     i_BigDecimal = rb_intern("BigDecimal");
+    i_freeze = rb_intern("freeze");
+    i_uminus = rb_intern("-@");
 }
 
 /*
diff --git a/ext/json/ext/parser/parser.h b/ext/json/ext/parser/parser.h
index e6cf7790..e3eb920c 100644
--- a/ext/json/ext/parser/parser.h
+++ b/ext/json/ext/parser/parser.h
@@ -37,6 +37,7 @@ typedef struct JSON_ParserStruct {
     int allow_nan;
     int parsing_name;
     int symbolize_names;
+    int freeze;
     VALUE object_class;
     VALUE array_class;
     VALUE decimal_class;
diff --git a/ext/json/ext/parser/parser.rl b/ext/json/ext/parser/parser.rl
index 00a35bde..46290520 100644
--- a/ext/json/ext/parser/parser.rl
+++ b/ext/json/ext/parser/parser.rl
@@ -95,7 +95,7 @@ static ID i_json_creatable_p, i_json_create, i_create_id, i_create_additions,
           i_chr, i_max_nesting, i_allow_nan, i_symbolize_names,
           i_object_class, i_array_class, i_decimal_class, i_key_p,
           i_deep_const_get, i_match, i_match_string, i_aset, i_aref,
-          i_leftshift, i_new, i_BigDecimal;
+          i_leftshift, i_new, i_BigDecimal, i_freeze, i_uminus;
 
 %%{
     machine JSON_common;
@@ -290,6 +290,10 @@ static char *JSON_parse_value(JSON_Parser *json, char *p, char *pe, VALUE *resul
     %% write init;
     %% write exec;
 
+    if (json->freeze) {
+        OBJ_FREEZE(*result);
+    }
+
     if (cs >= JSON_value_first_final) {
         return p;
     } else {
@@ -573,7 +577,22 @@ static char *JSON_parse_string(JSON_Parser *json, char *p, char *pe, VALUE *resu
     if (json->symbolize_names && json->parsing_name) {
       *result = rb_str_intern(*result);
     } else if (RB_TYPE_P(*result, T_STRING)) {
+# if STR_UMINUS_DEDUPE_FROZEN
+      if (json->freeze) {
+        // Starting from MRI 2.8 it is preferable to freeze the string
+        // before deduplication so that it can be interned directly
+        // otherwise it would be duplicated first which is wasteful.
+        *result = rb_funcall(rb_str_freeze(*result), i_uminus, 0);
+      }
+# elif STR_UMINUS_DEDUPE
+      if (json->freeze) {
+        // MRI 2.5 and older do not deduplicate strings that are already
+        // frozen.
+        *result = rb_funcall(*result, i_uminus, 0);
+      }
+# else
       rb_str_resize(*result, RSTRING_LEN(*result));
+# endif
     }
     if (cs >= JSON_string_first_final) {
         return p + 1;
@@ -681,6 +700,12 @@ static VALUE cParser_initialize(int argc, VALUE *argv, VALUE self)
             } else {
                 json->symbolize_names = 0;
             }
+            tmp = ID2SYM(i_freeze);
+            if (option_given_p(opts, tmp)) {
+                json->freeze = RTEST(rb_hash_aref(opts, tmp)) ? 1 : 0;
+            } else {
+                json->freeze = 0;
+            }
             tmp = ID2SYM(i_create_additions);
             if (option_given_p(opts, tmp)) {
                 json->create_additions = RTEST(rb_hash_aref(opts, tmp));
@@ -886,6 +911,8 @@ void Init_parser(void)
     i_leftshift = rb_intern("<<");
     i_new = rb_intern("new");
     i_BigDecimal = rb_intern("BigDecimal");
+    i_freeze = rb_intern("freeze");
+    i_uminus = rb_intern("-@");
 }
 
 /*
diff --git a/ext/json/extconf.rb b/ext/json/extconf.rb
index 7595d58a..8a99b6a5 100644
--- a/ext/json/extconf.rb
+++ b/ext/json/extconf.rb
@@ -1,2 +1,3 @@
 require 'mkmf'
+
 create_makefile('json')
diff --git a/java/src/json/ext/Parser.java b/java/src/json/ext/Parser.java
index 647afca8..ef283932 100644
--- a/java/src/json/ext/Parser.java
+++ b/java/src/json/ext/Parser.java
@@ -52,6 +52,7 @@ public class Parser extends RubyObject {
     private int maxNesting;
     private boolean allowNaN;
     private boolean symbolizeNames;
+    private boolean freeze;
     private RubyClass objectClass;
     private RubyClass arrayClass;
     private RubyClass decimalClass;
@@ -160,6 +161,7 @@ public IRubyObject initialize(ThreadContext context, IRubyObject[] args) {
         this.maxNesting      = opts.getInt("max_nesting", DEFAULT_MAX_NESTING);
         this.allowNaN        = opts.getBool("allow_nan", false);
         this.symbolizeNames  = opts.getBool("symbolize_names", false);
+        this.freeze          = opts.getBool("freeze", false);
         this.createId        = opts.getString("create_id", getCreateId(context));
         this.createAdditions = opts.getBool("create_additions", false);
         this.objectClass     = opts.getClass("object_class", runtime.getHash());
@@ -313,11 +315,11 @@ private Ruby getRuntime() {
         }
 
         
-// line 339 "Parser.rl"
+// line 341 "Parser.rl"
 
 
         
-// line 321 "Parser.java"
+// line 323 "Parser.java"
 private static byte[] init__JSON_value_actions_0()
 {
 	return new byte [] {
@@ -431,7 +433,7 @@ private static byte[] init__JSON_value_from_state_actions_0()
 static final int JSON_value_en_main = 1;
 
 
-// line 445 "Parser.rl"
+// line 447 "Parser.rl"
 
 
         void parseValue(ParserResult res, int p, int pe) {
@@ -439,14 +441,14 @@ void parseValue(ParserResult res, int p, int pe) {
             IRubyObject result = null;
 
             
-// line 443 "Parser.java"
+// line 445 "Parser.java"
 	{
 	cs = JSON_value_start;
 	}
 
-// line 452 "Parser.rl"
+// line 454 "Parser.rl"
             
-// line 450 "Parser.java"
+// line 452 "Parser.java"
 	{
 	int _klen;
 	int _trans = 0;
@@ -472,13 +474,13 @@ void parseValue(ParserResult res, int p, int pe) {
 	while ( _nacts-- > 0 ) {
 		switch ( _JSON_value_actions[_acts++] ) {
 	case 9:
-// line 430 "Parser.rl"
+// line 432 "Parser.rl"
 	{
                 p--;
                 { p += 1; _goto_targ = 5; if (true)  continue _goto;}
             }
 	break;
-// line 482 "Parser.java"
+// line 484 "Parser.java"
 		}
 	}
 
@@ -541,25 +543,25 @@ else if ( data[p] > _JSON_value_trans_keys[_mid+1] )
 			switch ( _JSON_value_actions[_acts++] )
 			{
 	case 0:
-// line 347 "Parser.rl"
+// line 349 "Parser.rl"
 	{
                 result = getRuntime().getNil();
             }
 	break;
 	case 1:
-// line 350 "Parser.rl"
+// line 352 "Parser.rl"
 	{
                 result = getRuntime().getFalse();
             }
 	break;
 	case 2:
-// line 353 "Parser.rl"
+// line 355 "Parser.rl"
 	{
                 result = getRuntime().getTrue();
             }
 	break;
 	case 3:
-// line 356 "Parser.rl"
+// line 358 "Parser.rl"
 	{
                 if (parser.allowNaN) {
                     result = getConstant(CONST_NAN);
@@ -569,7 +571,7 @@ else if ( data[p] > _JSON_value_trans_keys[_mid+1] )
             }
 	break;
 	case 4:
-// line 363 "Parser.rl"
+// line 365 "Parser.rl"
 	{
                 if (parser.allowNaN) {
                     result = getConstant(CONST_INFINITY);
@@ -579,7 +581,7 @@ else if ( data[p] > _JSON_value_trans_keys[_mid+1] )
             }
 	break;
 	case 5:
-// line 370 "Parser.rl"
+// line 372 "Parser.rl"
 	{
                 if (pe > p + 8 &&
                     absSubSequence(p, p + 9).equals(JSON_MINUS_INFINITY)) {
@@ -608,7 +610,7 @@ else if ( data[p] > _JSON_value_trans_keys[_mid+1] )
             }
 	break;
 	case 6:
-// line 396 "Parser.rl"
+// line 398 "Parser.rl"
 	{
                 parseString(res, p, pe);
                 if (res.result == null) {
@@ -621,7 +623,7 @@ else if ( data[p] > _JSON_value_trans_keys[_mid+1] )
             }
 	break;
 	case 7:
-// line 406 "Parser.rl"
+// line 408 "Parser.rl"
 	{
                 currentNesting++;
                 parseArray(res, p, pe);
@@ -636,7 +638,7 @@ else if ( data[p] > _JSON_value_trans_keys[_mid+1] )
             }
 	break;
 	case 8:
-// line 418 "Parser.rl"
+// line 420 "Parser.rl"
 	{
                 currentNesting++;
                 parseObject(res, p, pe);
@@ -650,7 +652,7 @@ else if ( data[p] > _JSON_value_trans_keys[_mid+1] )
                 }
             }
 	break;
-// line 654 "Parser.java"
+// line 656 "Parser.java"
 			}
 		}
 	}
@@ -670,9 +672,12 @@ else if ( data[p] > _JSON_value_trans_keys[_mid+1] )
 	break; }
 	}
 
-// line 453 "Parser.rl"
+// line 455 "Parser.rl"
 
             if (cs >= JSON_value_first_final && result != null) {
+                if (parser.freeze) {
+                  result.setFrozen(true);
+                }
                 res.update(result, p);
             } else {
                 res.update(null, p);
@@ -680,7 +685,7 @@ else if ( data[p] > _JSON_value_trans_keys[_mid+1] )
         }
 
         
-// line 684 "Parser.java"
+// line 689 "Parser.java"
 private static byte[] init__JSON_integer_actions_0()
 {
 	return new byte [] {
@@ -779,7 +784,7 @@ private static byte[] init__JSON_integer_trans_actions_0()
 static final int JSON_integer_en_main = 1;
 
 
-// line 472 "Parser.rl"
+// line 477 "Parser.rl"
 
 
         void parseInteger(ParserResult res, int p, int pe) {
@@ -797,15 +802,15 @@ int parseIntegerInternal(int p, int pe) {
             int cs = EVIL;
 
             
-// line 801 "Parser.java"
+// line 806 "Parser.java"
 	{
 	cs = JSON_integer_start;
 	}
 
-// line 489 "Parser.rl"
+// line 494 "Parser.rl"
             int memo = p;
             
-// line 809 "Parser.java"
+// line 814 "Parser.java"
 	{
 	int _klen;
 	int _trans = 0;
@@ -886,13 +891,13 @@ else if ( data[p] > _JSON_integer_trans_keys[_mid+1] )
 			switch ( _JSON_integer_actions[_acts++] )
 			{
 	case 0:
-// line 466 "Parser.rl"
+// line 471 "Parser.rl"
 	{
                 p--;
                 { p += 1; _goto_targ = 5; if (true)  continue _goto;}
             }
 	break;
-// line 896 "Parser.java"
+// line 901 "Parser.java"
 			}
 		}
 	}
@@ -912,7 +917,7 @@ else if ( data[p] > _JSON_integer_trans_keys[_mid+1] )
 	break; }
 	}
 
-// line 491 "Parser.rl"
+// line 496 "Parser.rl"
 
             if (cs < JSON_integer_first_final) {
                 return -1;
@@ -934,7 +939,7 @@ RubyInteger bytesToInum(Ruby runtime, ByteList num) {
         }
 
         
-// line 938 "Parser.java"
+// line 943 "Parser.java"
 private static byte[] init__JSON_float_actions_0()
 {
 	return new byte [] {
@@ -1036,7 +1041,7 @@ private static byte[] init__JSON_float_trans_actions_0()
 static final int JSON_float_en_main = 1;
 
 
-// line 526 "Parser.rl"
+// line 531 "Parser.rl"
 
 
         void parseFloat(ParserResult res, int p, int pe) {
@@ -1056,15 +1061,15 @@ int parseFloatInternal(int p, int pe) {
             int cs = EVIL;
 
             
-// line 1060 "Parser.java"
+// line 1065 "Parser.java"
 	{
 	cs = JSON_float_start;
 	}
 
-// line 545 "Parser.rl"
+// line 550 "Parser.rl"
             int memo = p;
             
-// line 1068 "Parser.java"
+// line 1073 "Parser.java"
 	{
 	int _klen;
 	int _trans = 0;
@@ -1145,13 +1150,13 @@ else if ( data[p] > _JSON_float_trans_keys[_mid+1] )
 			switch ( _JSON_float_actions[_acts++] )
 			{
 	case 0:
-// line 517 "Parser.rl"
+// line 522 "Parser.rl"
 	{
                 p--;
                 { p += 1; _goto_targ = 5; if (true)  continue _goto;}
             }
 	break;
-// line 1155 "Parser.java"
+// line 1160 "Parser.java"
 			}
 		}
 	}
@@ -1171,7 +1176,7 @@ else if ( data[p] > _JSON_float_trans_keys[_mid+1] )
 	break; }
 	}
 
-// line 547 "Parser.rl"
+// line 552 "Parser.rl"
 
             if (cs < JSON_float_first_final) {
                 return -1;
@@ -1194,7 +1199,7 @@ IRubyObject createCustomDecimal(int p, int new_p) {
         }
 
         
-// line 1198 "Parser.java"
+// line 1203 "Parser.java"
 private static byte[] init__JSON_string_actions_0()
 {
 	return new byte [] {
@@ -1296,7 +1301,7 @@ private static byte[] init__JSON_string_trans_actions_0()
 static final int JSON_string_en_main = 1;
 
 
-// line 599 "Parser.rl"
+// line 604 "Parser.rl"
 
 
         void parseString(ParserResult res, int p, int pe) {
@@ -1304,15 +1309,15 @@ void parseString(ParserResult res, int p, int pe) {
             IRubyObject result = null;
 
             
-// line 1308 "Parser.java"
+// line 1313 "Parser.java"
 	{
 	cs = JSON_string_start;
 	}
 
-// line 606 "Parser.rl"
+// line 611 "Parser.rl"
             int memo = p;
             
-// line 1316 "Parser.java"
+// line 1321 "Parser.java"
 	{
 	int _klen;
 	int _trans = 0;
@@ -1393,7 +1398,7 @@ else if ( data[p] > _JSON_string_trans_keys[_mid+1] )
 			switch ( _JSON_string_actions[_acts++] )
 			{
 	case 0:
-// line 574 "Parser.rl"
+// line 579 "Parser.rl"
 	{
                 int offset = byteList.begin();
                 ByteList decoded = decoder.decode(byteList, memo + 1 - offset,
@@ -1408,13 +1413,13 @@ else if ( data[p] > _JSON_string_trans_keys[_mid+1] )
             }
 	break;
 	case 1:
-// line 587 "Parser.rl"
+// line 592 "Parser.rl"
 	{
                 p--;
                 { p += 1; _goto_targ = 5; if (true)  continue _goto;}
             }
 	break;
-// line 1418 "Parser.java"
+// line 1423 "Parser.java"
 			}
 		}
 	}
@@ -1434,7 +1439,7 @@ else if ( data[p] > _JSON_string_trans_keys[_mid+1] )
 	break; }
 	}
 
-// line 608 "Parser.rl"
+// line 613 "Parser.rl"
 
             if (parser.createAdditions) {
                 RubyHash matchString = parser.match_string;
@@ -1463,16 +1468,23 @@ public void visit(IRubyObject pattern, IRubyObject klass) {
 
             if (cs >= JSON_string_first_final && result != null) {
                 if (result instanceof RubyString) {
-                  ((RubyString)result).force_encoding(context, info.utf8.get());
+                  RubyString string = (RubyString)result;
+                  string.force_encoding(context, info.utf8.get());
+                  if (parser.freeze) {
+                     string.setFrozen(true);
+                     string = getRuntime().freezeAndDedupString(string);
+                  }
+                  res.update(string, p + 1);
+                } else {
+                  res.update(result, p + 1);
                 }
-                res.update(result, p + 1);
             } else {
                 res.update(null, p + 1);
             }
         }
 
         
-// line 1476 "Parser.java"
+// line 1488 "Parser.java"
 private static byte[] init__JSON_array_actions_0()
 {
 	return new byte [] {
@@ -1585,7 +1597,7 @@ private static byte[] init__JSON_array_trans_actions_0()
 static final int JSON_array_en_main = 1;
 
 
-// line 681 "Parser.rl"
+// line 693 "Parser.rl"
 
 
         void parseArray(ParserResult res, int p, int pe) {
@@ -1605,14 +1617,14 @@ void parseArray(ParserResult res, int p, int pe) {
             }
 
             
-// line 1609 "Parser.java"
+// line 1621 "Parser.java"
 	{
 	cs = JSON_array_start;
 	}
 
-// line 700 "Parser.rl"
+// line 712 "Parser.rl"
             
-// line 1616 "Parser.java"
+// line 1628 "Parser.java"
 	{
 	int _klen;
 	int _trans = 0;
@@ -1693,7 +1705,7 @@ else if ( data[p] > _JSON_array_trans_keys[_mid+1] )
 			switch ( _JSON_array_actions[_acts++] )
 			{
 	case 0:
-// line 650 "Parser.rl"
+// line 662 "Parser.rl"
 	{
                 parseValue(res, p, pe);
                 if (res.result == null) {
@@ -1710,13 +1722,13 @@ else if ( data[p] > _JSON_array_trans_keys[_mid+1] )
             }
 	break;
 	case 1:
-// line 665 "Parser.rl"
+// line 677 "Parser.rl"
 	{
                 p--;
                 { p += 1; _goto_targ = 5; if (true)  continue _goto;}
             }
 	break;
-// line 1720 "Parser.java"
+// line 1732 "Parser.java"
 			}
 		}
 	}
@@ -1736,7 +1748,7 @@ else if ( data[p] > _JSON_array_trans_keys[_mid+1] )
 	break; }
 	}
 
-// line 701 "Parser.rl"
+// line 713 "Parser.rl"
 
             if (cs >= JSON_array_first_final) {
                 res.update(result, p + 1);
@@ -1746,7 +1758,7 @@ else if ( data[p] > _JSON_array_trans_keys[_mid+1] )
         }
 
         
-// line 1750 "Parser.java"
+// line 1762 "Parser.java"
 private static byte[] init__JSON_object_actions_0()
 {
 	return new byte [] {
@@ -1869,7 +1881,7 @@ private static byte[] init__JSON_object_trans_actions_0()
 static final int JSON_object_en_main = 1;
 
 
-// line 760 "Parser.rl"
+// line 772 "Parser.rl"
 
 
         void parseObject(ParserResult res, int p, int pe) {
@@ -1894,14 +1906,14 @@ void parseObject(ParserResult res, int p, int pe) {
             }
 
             
-// line 1898 "Parser.java"
+// line 1910 "Parser.java"
 	{
 	cs = JSON_object_start;
 	}
 
-// line 784 "Parser.rl"
+// line 796 "Parser.rl"
             
-// line 1905 "Parser.java"
+// line 1917 "Parser.java"
 	{
 	int _klen;
 	int _trans = 0;
@@ -1982,7 +1994,7 @@ else if ( data[p] > _JSON_object_trans_keys[_mid+1] )
 			switch ( _JSON_object_actions[_acts++] )
 			{
 	case 0:
-// line 715 "Parser.rl"
+// line 727 "Parser.rl"
 	{
                 parseValue(res, p, pe);
                 if (res.result == null) {
@@ -1999,7 +2011,7 @@ else if ( data[p] > _JSON_object_trans_keys[_mid+1] )
             }
 	break;
 	case 1:
-// line 730 "Parser.rl"
+// line 742 "Parser.rl"
 	{
                 parseString(res, p, pe);
                 if (res.result == null) {
@@ -2019,13 +2031,13 @@ else if ( data[p] > _JSON_object_trans_keys[_mid+1] )
             }
 	break;
 	case 2:
-// line 748 "Parser.rl"
+// line 760 "Parser.rl"
 	{
                 p--;
                 { p += 1; _goto_targ = 5; if (true)  continue _goto;}
             }
 	break;
-// line 2029 "Parser.java"
+// line 2041 "Parser.java"
 			}
 		}
 	}
@@ -2045,7 +2057,7 @@ else if ( data[p] > _JSON_object_trans_keys[_mid+1] )
 	break; }
 	}
 
-// line 785 "Parser.rl"
+// line 797 "Parser.rl"
 
             if (cs < JSON_object_first_final) {
                 res.update(null, p + 1);
@@ -2078,7 +2090,7 @@ else if ( data[p] > _JSON_object_trans_keys[_mid+1] )
         }
 
         
-// line 2082 "Parser.java"
+// line 2094 "Parser.java"
 private static byte[] init__JSON_actions_0()
 {
 	return new byte [] {
@@ -2181,7 +2193,7 @@ private static byte[] init__JSON_trans_actions_0()
 static final int JSON_en_main = 1;
 
 
-// line 836 "Parser.rl"
+// line 848 "Parser.rl"
 
 
         public IRubyObject parseImplemetation() {
@@ -2191,16 +2203,16 @@ public IRubyObject parseImplemetation() {
             ParserResult res = new ParserResult();
 
             
-// line 2195 "Parser.java"
+// line 2207 "Parser.java"
 	{
 	cs = JSON_start;
 	}
 
-// line 845 "Parser.rl"
+// line 857 "Parser.rl"
             p = byteList.begin();
             pe = p + byteList.length();
             
-// line 2204 "Parser.java"
+// line 2216 "Parser.java"
 	{
 	int _klen;
 	int _trans = 0;
@@ -2281,7 +2293,7 @@ else if ( data[p] > _JSON_trans_keys[_mid+1] )
 			switch ( _JSON_actions[_acts++] )
 			{
 	case 0:
-// line 822 "Parser.rl"
+// line 834 "Parser.rl"
 	{
                 parseValue(res, p, pe);
                 if (res.result == null) {
@@ -2293,7 +2305,7 @@ else if ( data[p] > _JSON_trans_keys[_mid+1] )
                 }
             }
 	break;
-// line 2297 "Parser.java"
+// line 2309 "Parser.java"
 			}
 		}
 	}
@@ -2313,7 +2325,7 @@ else if ( data[p] > _JSON_trans_keys[_mid+1] )
 	break; }
 	}
 
-// line 848 "Parser.rl"
+// line 860 "Parser.rl"
 
             if (cs >= JSON_first_final && p == pe) {
                 return result;
diff --git a/java/src/json/ext/Parser.rl b/java/src/json/ext/Parser.rl
index c0c72adc..f670bad1 100644
--- a/java/src/json/ext/Parser.rl
+++ b/java/src/json/ext/Parser.rl
@@ -50,6 +50,7 @@ public class Parser extends RubyObject {
     private int maxNesting;
     private boolean allowNaN;
     private boolean symbolizeNames;
+    private boolean freeze;
     private RubyClass objectClass;
     private RubyClass arrayClass;
     private RubyClass decimalClass;
@@ -158,6 +159,7 @@ public class Parser extends RubyObject {
         this.maxNesting      = opts.getInt("max_nesting", DEFAULT_MAX_NESTING);
         this.allowNaN        = opts.getBool("allow_nan", false);
         this.symbolizeNames  = opts.getBool("symbolize_names", false);
+        this.freeze          = opts.getBool("freeze", false);
         this.createId        = opts.getString("create_id", getCreateId(context));
         this.createAdditions = opts.getBool("create_additions", false);
         this.objectClass     = opts.getClass("object_class", runtime.getHash());
@@ -452,6 +454,9 @@ public class Parser extends RubyObject {
             %% write exec;
 
             if (cs >= JSON_value_first_final && result != null) {
+                if (parser.freeze) {
+                  result.setFrozen(true);
+                }
                 res.update(result, p);
             } else {
                 res.update(null, p);
@@ -633,9 +638,16 @@ public class Parser extends RubyObject {
 
             if (cs >= JSON_string_first_final && result != null) {
                 if (result instanceof RubyString) {
-                  ((RubyString)result).force_encoding(context, info.utf8.get());
+                  RubyString string = (RubyString)result;
+                  string.force_encoding(context, info.utf8.get());
+                  if (parser.freeze) {
+                     string.setFrozen(true);
+                     string = getRuntime().freezeAndDedupString(string);
+                  }
+                  res.update(string, p + 1);
+                } else {
+                  res.update(result, p + 1);
                 }
-                res.update(result, p + 1);
             } else {
                 res.update(null, p + 1);
             }
diff --git a/lib/json/pure/parser.rb b/lib/json/pure/parser.rb
index 6f37e0cb..d795a3b9 100644
--- a/lib/json/pure/parser.rb
+++ b/lib/json/pure/parser.rb
@@ -61,6 +61,8 @@ class Parser < StringScanner
       # * *allow_nan*: If set to true, allow NaN, Infinity and -Infinity in
       #   defiance of RFC 7159 to be parsed by the Parser. This option defaults
       #   to false.
+      # * *freeze*: If set to true, all parsed objects will be frozen. Parsed
+      #   string will be deduplicated if possible.
       # * *symbolize_names*: If set to true, returns symbols for the names
       #   (keys) in a JSON object. Otherwise strings are returned, which is
       #   also the default. It's not possible to use this option in
@@ -86,6 +88,7 @@ def initialize(source, opts = {})
         end
         @allow_nan = !!opts[:allow_nan]
         @symbolize_names = !!opts[:symbolize_names]
+        @freeze = !!opts[:freeze]
         if opts.key?(:create_additions)
           @create_additions = !!opts[:create_additions]
         else
@@ -120,6 +123,7 @@ def parse
           obj = parse_value
           UNPARSED.equal?(obj) and raise ParserError,
             "source is not valid JSON!"
+          obj.freeze if @freeze
         end
         while !eos? && skip(IGNORE) do end
         eos? or raise ParserError, "source is not valid JSON!"
@@ -161,6 +165,7 @@ def convert_encoding(source)
         EMPTY_8BIT_STRING.force_encoding Encoding::ASCII_8BIT
       end
 
+      STR_UMINUS = ''.respond_to?(:-@)
       def parse_string
         if scan(STRING)
           return '' if self[1].empty?
@@ -180,6 +185,15 @@ def parse_string
           if string.respond_to?(:force_encoding)
             string.force_encoding(::Encoding::UTF_8)
           end
+
+          if @freeze
+            if STR_UMINUS
+              string = -string
+            else
+              string.freeze
+            end
+          end
+
           if @create_additions and @match_string
             for (regexp, klass) in @match_string
               klass.json_creatable? or next
diff --git a/tests/json_parser_test.rb b/tests/json_parser_test.rb
index 514441ef..e29f3f12 100644
--- a/tests/json_parser_test.rb
+++ b/tests/json_parser_test.rb
@@ -218,6 +218,17 @@ def test_symbolize_names
     end
   end
 
+  def test_freeze
+    assert_predicate parse('{}', :freeze => true), :frozen?
+    assert_predicate parse('[]', :freeze => true), :frozen?
+    assert_predicate parse('"foo"', :freeze => true), :frozen?
+    
+    if string_deduplication_available?
+      assert_same -'foo', parse('"foo"', :freeze => true)
+      assert_same -'foo', parse('{"foo": 1}', :freeze => true).keys.first
+    end
+  end
+
   def test_parse_comments
     json = <<EOT
 {
@@ -468,6 +479,16 @@ def test_parsing_frozen_ascii8bit_string
 
   private
 
+  def string_deduplication_available?
+    r1 = rand.to_s
+    r2 = r1.dup
+    begin
+      (-r1).equal?(-r2)
+    rescue NoMethodError
+      false # No String#-@
+    end
+  end
+
   def assert_equal_float(expected, actual, delta = 1e-2)
     Array === expected and expected = expected.first
     Array === actual and actual = actual.first