diff --git a/CHANGELOG.md b/CHANGELOG.md
index 75e47583..f6dcecad 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # CHANGELOG
 
+## 3.11.0 - 2020-01-12
+
+- Added `:compat_bigdecimal` to support the JSON gem `:decimal_class` undocumented option.
+
+- Reverted the use of `:bigdecimal_load` for `:compat` mode.
+
 ## 3.10.18 - 2020-12-25
 
 - Fix modes table by marking compat mode `:bigdecimal_load` instead of `:bigdecimal_as_decimal`.
diff --git a/ext/oj/mimic_json.c b/ext/oj/mimic_json.c
index 3119fd4f..37efb9f7 100644
--- a/ext/oj/mimic_json.c
+++ b/ext/oj/mimic_json.c
@@ -364,7 +364,6 @@ mimic_generate_core(int argc, VALUE *argv, Options copts) {
     struct _out	out;
     VALUE	rstr;
 
-    // TBD
     memset(buf, 0, sizeof(buf));
 
     out.buf = buf;
@@ -510,6 +509,7 @@ mimic_parse_core(int argc, VALUE *argv, VALUE self, bool bang) {
     pi.options.create_ok = No;
     pi.options.allow_nan = (bang ? Yes : No);
     pi.options.nilnil = No;
+    pi.options.bigdec_load = RubyDec;
     pi.options.mode = CompatMode;
     pi.max_depth = 100;
 
@@ -560,14 +560,7 @@ mimic_parse_core(int argc, VALUE *argv, VALUE self, bool bang) {
 	    }
 	}
 	if (Qtrue == rb_funcall(ropts, oj_has_key_id, 1, oj_decimal_class_sym)) {
-	    v = rb_hash_lookup(ropts, oj_decimal_class_sym);
-	    if (rb_cFloat == v) {
-		pi.options.bigdec_load = FloatDec;
-	    } else if (oj_bigdecimal_class == v) {
-		pi.options.bigdec_load = BigDec;
-	    } else if (Qnil == v) {
-		pi.options.bigdec_load = AutoDec;
-	    }
+	    pi.options.compat_bigdec = (oj_bigdecimal_class == rb_hash_lookup(ropts, oj_decimal_class_sym));
 	}
 	v = rb_hash_lookup(ropts, oj_max_nesting_sym);
 	if (Qtrue == v) {
@@ -693,6 +686,7 @@ static struct _options	mimic_object_to_json_options = {
     RubyTime,	// time_format
     No,		// bigdec_as_num
     RubyDec,	// bigdec_load
+    false,	// compat_bigdec
     No,		// to_hash
     No,		// to_json
     No,		// as_json
diff --git a/ext/oj/oj.c b/ext/oj/oj.c
index e55b41c8..cc9a7bd0 100644
--- a/ext/oj/oj.c
+++ b/ext/oj/oj.c
@@ -107,6 +107,7 @@ static VALUE	bigdecimal_load_sym;
 static VALUE	bigdecimal_sym;
 static VALUE	circular_sym;
 static VALUE	class_cache_sym;
+static VALUE	compat_bigdecimal_sym;
 static VALUE	compat_sym;
 static VALUE	create_id_sym;
 static VALUE	custom_sym;
@@ -168,6 +169,7 @@ struct _options	oj_default_options = {
     UnixTime,	// time_format
     NotSet,	// bigdec_as_num
     AutoDec,	// bigdec_load
+    false,	// compat_bigdec
     No,		// to_hash
     No,		// to_json
     No,		// as_json
@@ -230,6 +232,7 @@ struct _options	oj_default_options = {
  * - *:time_format* [_:unix_|_:unix_zone_|_:xmlschema_|_:ruby_] time format when dumping
  * - *:bigdecimal_as_decimal* [_Boolean_|_nil_] dump BigDecimal as a decimal number or as a String
  * - *:bigdecimal_load* [_:bigdecimal_|_:float_|_:auto_|_:fast_] load decimals as BigDecimal instead of as a Float. :auto pick the most precise for the number of digits. :float should be the same as ruby. :fast may require rounding but is must faster.
+ * - *:compat_bigdecimal* [_true_|_false_] load decimals as BigDecimal instead of as a Float when in compat or rails mode.
  * - *:create_id* [_String_|_nil_] create id for json compatible object encoding, default is 'json_class'
  * - *:create_additions* [_Boolean_|_nil_] if true allow creation of instances using create_id on load.
  * - *:second_precision* [_Fixnum_|_nil_] number of digits after the decimal when dumping the seconds portion of time
@@ -334,6 +337,7 @@ get_def_opts(VALUE self) {
     case AutoDec:
     default:		rb_hash_aset(opts, bigdecimal_load_sym, auto_sym);	break;
     }
+    rb_hash_aset(opts, compat_bigdecimal_sym, oj_default_options.compat_bigdec ? Qtrue : Qfalse);
     rb_hash_aset(opts, create_id_sym, (NULL == oj_default_options.create_id) ? Qnil : rb_str_new2(oj_default_options.create_id));
     rb_hash_aset(opts, oj_space_sym, (0 == oj_default_options.dump_opts.after_size) ? Qnil : rb_str_new2(oj_default_options.dump_opts.after_sep));
     rb_hash_aset(opts, oj_space_before_sym, (0 == oj_default_options.dump_opts.before_size) ? Qnil : rb_str_new2(oj_default_options.dump_opts.before_sep));
@@ -379,6 +383,7 @@ get_def_opts(VALUE self) {
  *   - *:escape* [_:newline_|_:json_|_:xss_safe_|_:ascii_|_unicode_xss_|_nil_] mode encodes all high-bit characters as escaped sequences if :ascii, :json is standand UTF-8 JSON encoding, :newline is the same as :json but newlines are not escaped, :unicode_xss allows unicode but escapes &, <, and >, and any \u20xx characters along with some others, and :xss_safe escapes &, <, and >, and some others.
  *   - *:bigdecimal_as_decimal* [_Boolean_|_nil_] dump BigDecimal as a decimal number or as a String.
  *   - *:bigdecimal_load* [_:bigdecimal_|_:float_|_:auto_|_nil_] load decimals as BigDecimal instead of as a Float. :auto pick the most precise for the number of digits.
+ *   - *:compat_bigdecimal* [_true_|_false_] load decimals as BigDecimal instead of as a Float in compat mode.
  *   - *:mode* [_:object_|_:strict_|_:compat_|_:null_|_:custom_|_:rails_|_:wab_] load and dump mode to use for JSON :strict raises an exception when a non-supported Object is encountered. :compat attempts to extract variable values from an Object using to_json() or to_hash() then it walks the Object's variables if neither is found. The :object mode ignores to_hash() and to_json() methods and encodes variables using code internal to the Oj gem. The :null mode ignores non-supported Objects and replaces them with a null. The :custom mode honors all dump options. The :rails more mimics rails and Active behavior.
  *   - *:time_format* [_:unix_|_:xmlschema_|_:ruby_] time format when dumping in :compat mode :unix decimal number denoting the number of seconds since 1/1/1970, :unix_zone decimal number denoting the number of seconds since 1/1/1970 plus the utc_offset in the exponent, :xmlschema date-time format taken from XML Schema as a String, :ruby Time.to_s formatted String.
  *   - *:create_id* [_String_|_nil_] create id for json compatible object encoding
@@ -582,19 +587,21 @@ oj_parse_options(VALUE ropts, Options copts) {
 	    rb_raise(rb_eArgError, ":bigdecimal_load must be :bigdecimal, :float, or :auto.");
 	}
     }
+    if (Qnil != (v = rb_hash_lookup(ropts, compat_bigdecimal_sym))) {
+	copts->compat_bigdec = (Qtrue == v);
+    }
     if (Qtrue == rb_funcall(ropts, oj_has_key_id, 1, oj_decimal_class_sym)) {
 	v = rb_hash_lookup(ropts, oj_decimal_class_sym);
 	if (rb_cFloat == v) {
-	    copts->bigdec_load = FloatDec;
+	    copts->compat_bigdec = FloatDec;
 	} else if (oj_bigdecimal_class == v) {
- 	    copts->bigdec_load = BigDec;
+ 	    copts->compat_bigdec = BigDec;
 	} else if (Qnil == v) {
-	    copts->bigdec_load = AutoDec;
+	    copts->compat_bigdec = AutoDec;
 	} else {
 	    rb_raise(rb_eArgError, ":decimal_class must be BigDecimal, Float, or nil.");
 	}
    }
-
     if (Qtrue == rb_funcall(ropts, oj_has_key_id, 1, create_id_sym)) {
 	v = rb_hash_lookup(ropts, create_id_sym);
 	if (Qnil == v) {
@@ -1663,6 +1670,7 @@ Init_oj() {
     bigdecimal_sym = ID2SYM(rb_intern("bigdecimal"));		rb_gc_register_address(&bigdecimal_sym);
     circular_sym = ID2SYM(rb_intern("circular"));		rb_gc_register_address(&circular_sym);
     class_cache_sym = ID2SYM(rb_intern("class_cache"));		rb_gc_register_address(&class_cache_sym);
+    compat_bigdecimal_sym = ID2SYM(rb_intern("compat_bigdecimal"));rb_gc_register_address(&compat_bigdecimal_sym);
     compat_sym = ID2SYM(rb_intern("compat"));			rb_gc_register_address(&compat_sym);
     create_id_sym = ID2SYM(rb_intern("create_id"));		rb_gc_register_address(&create_id_sym);
     custom_sym = ID2SYM(rb_intern("custom"));			rb_gc_register_address(&custom_sym);
diff --git a/ext/oj/oj.h b/ext/oj/oj.h
index 002f6f60..6edf3dfc 100644
--- a/ext/oj/oj.h
+++ b/ext/oj/oj.h
@@ -135,6 +135,7 @@ typedef struct _options {
     char		time_format;	// TimeFormat
     char		bigdec_as_num;	// YesNo
     char		bigdec_load;	// BigLoad
+    char		compat_bigdec;	// boolean (0 or 1)
     char		to_hash;	// YesNo
     char		to_json;	// YesNo
     char		as_json;	// YesNo
diff --git a/ext/oj/parse.c b/ext/oj/parse.c
index bab42089..4047beb5 100644
--- a/ext/oj/parse.c
+++ b/ext/oj/parse.c
@@ -385,8 +385,13 @@ read_num(ParseInfo pi) {
     ni.nan = 0;
     ni.neg = 0;
     ni.has_exp = 0;
-    ni.no_big = (FloatDec == pi->options.bigdec_load || FastDec == pi->options.bigdec_load || RubyDec == pi->options.bigdec_load);
-    ni.bigdec_load = pi->options.bigdec_load;
+    if (CompatMode == pi->options.mode) {
+	ni.no_big = !pi->options.compat_bigdec;
+	ni.bigdec_load = pi->options.compat_bigdec;
+    } else {
+	ni.no_big = (FloatDec == pi->options.bigdec_load || FastDec == pi->options.bigdec_load || RubyDec == pi->options.bigdec_load);
+	ni.bigdec_load = pi->options.bigdec_load;
+    }
 
     if ('-' == *pi->cur) {
 	pi->cur++;
@@ -511,7 +516,11 @@ read_num(ParseInfo pi) {
 	    ni.nan = 1;
 	}
     }
-    if (BigDec == pi->options.bigdec_load) {
+    if (CompatMode == pi->options.mode) {
+	if (pi->options.compat_bigdec) {
+	    ni.big = 1;
+	}
+    } else if (BigDec == pi->options.bigdec_load) {
 	ni.big = 1;
     }
     if (0 == parent) {
diff --git a/ext/oj/sparse.c b/ext/oj/sparse.c
index 6ce743a1..46d7c8cd 100644
--- a/ext/oj/sparse.c
+++ b/ext/oj/sparse.c
@@ -400,8 +400,13 @@ read_num(ParseInfo pi) {
     ni.nan = 0;
     ni.neg = 0;
     ni.has_exp = 0;
-    ni.no_big = (FloatDec == pi->options.bigdec_load || FastDec == pi->options.bigdec_load || RubyDec == pi->options.bigdec_load);
-    ni.bigdec_load = pi->options.bigdec_load;
+    if (CompatMode == pi->options.mode) {
+	ni.no_big = !pi->options.compat_bigdec;
+	ni.bigdec_load = pi->options.compat_bigdec;
+    } else {
+	ni.no_big = (FloatDec == pi->options.bigdec_load || FastDec == pi->options.bigdec_load || RubyDec == pi->options.bigdec_load);
+	ni.bigdec_load = pi->options.bigdec_load;
+    }
 
     c = reader_get(&pi->rd);
     if ('-' == c) {
@@ -518,7 +523,11 @@ read_num(ParseInfo pi) {
 	    ni.nan = 1;
 	}
     }
-    if (BigDec == pi->options.bigdec_load) {
+    if (CompatMode == pi->options.mode) {
+	if (pi->options.compat_bigdec) {
+	    ni.big = 1;
+	}
+    } else if (BigDec == pi->options.bigdec_load) {
 	ni.big = 1;
     }
     add_num_value(pi, &ni);
@@ -541,15 +550,24 @@ read_nan(ParseInfo pi) {
     ni.infinity = 0;
     ni.nan = 1;
     ni.neg = 0;
-    ni.no_big = (FloatDec == pi->options.bigdec_load || FastDec == pi->options.bigdec_load || RubyDec == pi->options.bigdec_load);
-    ni.bigdec_load = pi->options.bigdec_load;
+    if (CompatMode == pi->options.mode) {
+	ni.no_big = !pi->options.compat_bigdec;
+	ni.bigdec_load = pi->options.compat_bigdec;
+    } else {
+	ni.no_big = (FloatDec == pi->options.bigdec_load || FastDec == pi->options.bigdec_load || RubyDec == pi->options.bigdec_load);
+	ni.bigdec_load = pi->options.bigdec_load;
+    }
 
     if ('a' != reader_get(&pi->rd) ||
 	('N' != (c = reader_get(&pi->rd)) && 'n' != c)) {
 	oj_set_error_at(pi, oj_parse_error_class, __FILE__, __LINE__, "not a number or other value");
 	return;
     }
-    if (BigDec == pi->options.bigdec_load) {
+    if (CompatMode == pi->options.mode) {
+	if (pi->options.compat_bigdec) {
+	    ni.big = 1;
+	}
+    } else if (BigDec == pi->options.bigdec_load) {
 	ni.big = 1;
     }
     add_num_value(pi, &ni);
@@ -739,8 +757,15 @@ oj_sparse2(ParseInfo pi) {
 		ni.infinity = 0;
 		ni.nan = 1;
 		ni.neg = 0;
-		ni.no_big = (FloatDec == pi->options.bigdec_load || RubyDec == pi->options.bigdec_load || FastDec == pi->options.bigdec_load);
-		ni.bigdec_load = pi->options.bigdec_load;
+		if (CompatMode == pi->options.mode) {
+		    ni.no_big = !pi->options.compat_bigdec;
+		    ni.bigdec_load = pi->options.compat_bigdec;
+		} else {
+		    ni.no_big = (FloatDec == pi->options.bigdec_load ||
+				 FastDec == pi->options.bigdec_load ||
+				 RubyDec == pi->options.bigdec_load);
+		    ni.bigdec_load = pi->options.bigdec_load;
+		}
 		add_num_value(pi, &ni);
 	    } else {
 		oj_set_error_at(pi, oj_parse_error_class, __FILE__, __LINE__, "invalid token");
diff --git a/lib/oj/version.rb b/lib/oj/version.rb
index a74b3845..99abcd3b 100644
--- a/lib/oj/version.rb
+++ b/lib/oj/version.rb
@@ -1,5 +1,5 @@
 
 module Oj
   # Current version of the module.
-  VERSION = '3.10.18'
+  VERSION = '3.11.0'
 end
diff --git a/pages/Modes.md b/pages/Modes.md
index 5bff950f..e332114d 100644
--- a/pages/Modes.md
+++ b/pages/Modes.md
@@ -95,7 +95,8 @@ information.
 | :ascii_only            | Boolean |       x |       x |       2 |       2 |       x |       x |         |
 | :auto_define           | Boolean |         |         |         |         |       x |       x |         |
 | :bigdecimal_as_decimal | Boolean |         |         |         |       3 |       x |       x |         |
-| :bigdecimal_load       | Boolean |         |         |       x |         |         |       x |         |
+| :bigdecimal_load       | Boolean |         |         |         |         |         |       x |         |
+| :compat_bigdecimal     | Boolean |         |         |       x |         |         |       x |         |
 | :circular              | Boolean |       x |       x |       x |       x |       x |       x |         |
 | :class_cache           | Boolean |         |         |         |         |       x |       x |         |
 | :create_additions      | Boolean |         |         |       x |       x |         |       x |         |
diff --git a/pages/Options.md b/pages/Options.md
index 07f8ed6a..515bf969 100644
--- a/pages/Options.md
+++ b/pages/Options.md
@@ -70,6 +70,14 @@ This can also be set with `:decimal_class` when used as a load or
 parse option to match the JSON gem. In that case either `Float`,
 `BigDecimal`, or `nil` can be provided.
 
+### :compat_bigdecimal [Boolean]
+
+Determines how to load decimals when in `:compat` mode.
+
+ - `true` convert all decimal numbers to BigDecimal.
+
+ - `false` convert all decimal numbers to Float.
+
 ### :circular [Boolean]
 
 Detect circular references while dumping. In :compat mode raise a
diff --git a/test/test_compat.rb b/test/test_compat.rb
index 68b094cc..47f2c15f 100755
--- a/test/test_compat.rb
+++ b/test/test_compat.rb
@@ -283,7 +283,7 @@ def test_bigdecimal
     assert_equal('"0.314159265358979323846e1"', json.downcase)
   end
 
-  def test_bigdecimal_load
+  def test_decimal_class
     big = BigDecimal('3.14159265358979323846')
     # :decimal_class is the undocumented feature.
     json = Oj.load('3.14159265358979323846', mode: :compat, decimal_class: BigDecimal)
diff --git a/test/test_various.rb b/test/test_various.rb
index 2730e1ee..7c304f89 100755
--- a/test/test_various.rb
+++ b/test/test_various.rb
@@ -120,6 +120,7 @@ def test_set_options
       escape_mode: :ascii,
       time_format: :unix_zone,
       bigdecimal_load: :float,
+      compat_bigdecimal: true,
       create_id: 'classy',
       create_additions: true,
       space: 'z',