diff --git a/ext/oj/cache.c b/ext/oj/cache.c
index ebaf10d9..131e0b6d 100644
--- a/ext/oj/cache.c
+++ b/ext/oj/cache.c
@@ -129,7 +129,9 @@ static void rehash(Cache c) {
 }
 
 void cache_free(Cache c) {
-    for (uint32_t i = 0; i < c->size; i++) {
+    uint32_t i;
+
+    for (i = 0; i < c->size; i++) {
         Slot next;
         Slot s;
 
@@ -147,7 +149,8 @@ void cache_mark(Cache c) {
 	uint32_t i;
 
         for (i = 0; i < c->size; i++) {
-            for (Slot s = c->slots[i]; NULL != s; s = s->next) {
+            Slot s;
+            for (s = c->slots[i]; NULL != s; s = s->next) {
                 rb_gc_mark(s->val);
             }
         }
diff --git a/ext/oj/debug.c b/ext/oj/debug.c
index bedcbd66..dc68532c 100644
--- a/ext/oj/debug.c
+++ b/ext/oj/debug.c
@@ -109,8 +109,9 @@ static void mark(struct _ojParser *p) {
 
 void oj_set_parser_debug(ojParser p) {
     Funcs end = p->funcs + 3;
+    Funcs f;
 
-    for (Funcs f = p->funcs; f < end; f++) {
+    for (f = p->funcs; f < end; f++) {
         f->add_null     = add_null;
         f->add_true     = add_true;
         f->add_false    = add_false;
diff --git a/ext/oj/parser.c b/ext/oj/parser.c
index 1fc3ea4e..c723428c 100644
--- a/ext/oj/parser.c
+++ b/ext/oj/parser.c
@@ -622,14 +622,14 @@ static void big_change(ojParser p) {
         buf_append_string(&p->buf, buf + len + 1, sizeof(buf) - len - 1);
         if (0 < p->num.exp) {
             int  x = p->num.exp;
-            int  d;
+            int  d, div;
             bool started = false;
 
             buf_append(&p->buf, 'e');
             if (0 < p->num.exp_neg) {
                 buf_append(&p->buf, '-');
             }
-            for (int div = 1000; 0 < div; div /= 10) {
+            for (div = 1000; 0 < div; div /= 10) {
                 d = x / div % 10;
                 if (started || 0 < d) {
                     buf_append(&p->buf, '0' + d);
@@ -646,6 +646,7 @@ static void big_change(ojParser p) {
 static void parse(ojParser p, const byte *json) {
     const byte *start;
     const byte *b = json;
+    int i;
 
 #if DEBUG
     printf("*** parse - mode: %c %s\n", p->map[256], (const char *)json);
@@ -1015,7 +1016,7 @@ static void parse(ojParser p, const byte *json) {
             }
             p->ri     = 0;
             *p->token = *b++;
-            for (int i = 1; i < 4; i++) {
+            for (i = 1; i < 4; i++) {
                 if ('\0' == *b) {
                     p->ri = i;
                     break;
@@ -1040,7 +1041,7 @@ static void parse(ojParser p, const byte *json) {
             }
             p->ri     = 0;
             *p->token = *b++;
-            for (int i = 1; i < 4; i++) {
+            for (i = 1; i < 4; i++) {
                 if ('\0' == *b) {
                     p->ri = i;
                     break;
@@ -1065,7 +1066,7 @@ static void parse(ojParser p, const byte *json) {
             }
             p->ri     = 0;
             *p->token = *b++;
-            for (int i = 1; i < 5; i++) {
+            for (i = 1; i < 5; i++) {
                 if ('\0' == *b) {
                     p->ri = i;
                     break;
diff --git a/ext/oj/saj2.c b/ext/oj/saj2.c
index 7fd8d6fe..74c7b6a3 100644
--- a/ext/oj/saj2.c
+++ b/ext/oj/saj2.c
@@ -182,8 +182,9 @@ static void add_str_key(ojParser p) {
 
 static void reset(ojParser p) {
     Funcs end = p->funcs + 3;
+    Funcs f;
 
-    for (Funcs f = p->funcs; f < end; f++) {
+    for (f = p->funcs; f < end; f++) {
         f->add_null     = noop;
         f->add_true     = noop;
         f->add_false    = noop;
@@ -312,13 +313,14 @@ static void mark(ojParser p) {
         return;
     }
     Delegate d = (Delegate)p->ctx;
+    VALUE *kp;
 
     cache_mark(d->str_cache);
     if (Qnil != d->handler) {
         rb_gc_mark(d->handler);
     }
     if (!d->cache_keys) {
-        for (VALUE *kp = d->keys; kp < d->tail; kp++) {
+        for (kp = d->keys; kp < d->tail; kp++) {
             rb_gc_mark(*kp);
         }
     }
diff --git a/ext/oj/usual.c b/ext/oj/usual.c
index a836816c..95af4f4f 100644
--- a/ext/oj/usual.c
+++ b/ext/oj/usual.c
@@ -323,6 +323,7 @@ static void open_array_key(ojParser p) {
 }
 
 static void close_object(ojParser p) {
+    VALUE *vp;
     Delegate d = (Delegate)p->ctx;
 
     d->ctail--;
@@ -333,7 +334,7 @@ static void close_object(ojParser p) {
     volatile VALUE obj  = rb_hash_new();
 
 #if HAVE_RB_HASH_BULK_INSERT
-    for (VALUE *vp = head; kp < d->ktail; kp++, vp += 2) {
+    for (vp = head; kp < d->ktail; kp++, vp += 2) {
         *vp = d->get_key(p, kp);
         if (sizeof(kp->buf) - 1 < (size_t)kp->len) {
             xfree(kp->key);
@@ -341,7 +342,7 @@ static void close_object(ojParser p) {
     }
     rb_hash_bulk_insert(d->vtail - head, head, obj);
 #else
-    for (VALUE *vp = head; kp < d->ktail; kp++, vp += 2) {
+    for (vp = head; kp < d->ktail; kp++, vp += 2) {
         rb_hash_aset(obj, d->get_key(p, kp), *(vp + 1));
         if (sizeof(kp->buf) - 1 < (size_t)kp->len) {
             xfree(kp->key);
@@ -355,6 +356,7 @@ static void close_object(ojParser p) {
 }
 
 static void close_object_class(ojParser p) {
+    VALUE *vp;
     Delegate d = (Delegate)p->ctx;
 
     d->ctail--;
@@ -364,7 +366,7 @@ static void close_object_class(ojParser p) {
     VALUE *        head = d->vhead + c->vi + 1;
     volatile VALUE obj  = rb_class_new_instance(0, NULL, d->hash_class);
 
-    for (VALUE *vp = head; kp < d->ktail; kp++, vp += 2) {
+    for (vp = head; kp < d->ktail; kp++, vp += 2) {
         rb_funcall(obj, hset_id, 2, d->get_key(p, kp), *(vp + 1));
         if (sizeof(kp->buf) - 1 < (size_t)kp->len) {
             xfree(kp->key);
@@ -377,6 +379,7 @@ static void close_object_class(ojParser p) {
 }
 
 static void close_object_create(ojParser p) {
+    VALUE *vp;
     Delegate d = (Delegate)p->ctx;
 
     d->ctail--;
@@ -391,7 +394,7 @@ static void close_object_create(ojParser p) {
         if (Qnil == d->hash_class) {
             obj = rb_hash_new();
 #if HAVE_RB_HASH_BULK_INSERT
-            for (VALUE *vp = head; kp < d->ktail; kp++, vp += 2) {
+            for (vp = head; kp < d->ktail; kp++, vp += 2) {
                 *vp = d->get_key(p, kp);
                 if (sizeof(kp->buf) - 1 < (size_t)kp->len) {
                     xfree(kp->key);
@@ -399,7 +402,7 @@ static void close_object_create(ojParser p) {
             }
             rb_hash_bulk_insert(d->vtail - head, head, obj);
 #else
-            for (VALUE *vp = head; kp < d->ktail; kp++, vp += 2) {
+            for (vp = head; kp < d->ktail; kp++, vp += 2) {
                 rb_hash_aset(obj, d->get_key(p, kp), *(vp + 1));
                 if (sizeof(kp->buf) - 1 < (size_t)kp->len) {
                     xfree(kp->key);
@@ -408,7 +411,7 @@ static void close_object_create(ojParser p) {
 #endif
         } else {
             obj = rb_class_new_instance(0, NULL, d->hash_class);
-            for (VALUE *vp = head; kp < d->ktail; kp++, vp += 2) {
+            for (vp = head; kp < d->ktail; kp++, vp += 2) {
                 rb_funcall(obj, hset_id, 2, d->get_key(p, kp), *(vp + 1));
                 if (sizeof(kp->buf) - 1 < (size_t)kp->len) {
                     xfree(kp->key);
@@ -423,7 +426,7 @@ static void close_object_create(ojParser p) {
             volatile VALUE arg = rb_hash_new();
 
 #if HAVE_RB_HASH_BULK_INSERT
-            for (VALUE *vp = head; kp < d->ktail; kp++, vp += 2) {
+            for (vp = head; kp < d->ktail; kp++, vp += 2) {
                 *vp = d->get_key(p, kp);
                 if (sizeof(kp->buf) - 1 < (size_t)kp->len) {
                     xfree(kp->key);
@@ -431,7 +434,7 @@ static void close_object_create(ojParser p) {
             }
             rb_hash_bulk_insert(d->vtail - head, head, arg);
 #else
-            for (VALUE *vp = head; kp < d->ktail; kp++, vp += 2) {
+            for (vp = head; kp < d->ktail; kp++, vp += 2) {
                 rb_hash_aset(arg, d->get_key(p, kp), *(vp + 1));
                 if (sizeof(kp->buf) - 1 < (size_t)kp->len) {
                     xfree(kp->key);
@@ -441,7 +444,7 @@ static void close_object_create(ojParser p) {
             obj = rb_funcall(clas, oj_json_create_id, 1, arg);
         } else {
             obj = rb_class_new_instance(0, NULL, clas);
-            for (VALUE *vp = head; kp < d->ktail; kp++, vp += 2) {
+            for (vp = head; kp < d->ktail; kp++, vp += 2) {
                 rb_ivar_set(obj, get_attr_id(p, kp), *(vp + 1));
                 if (sizeof(kp->buf) - 1 < (size_t)kp->len) {
                     xfree(kp->key);
@@ -468,13 +471,14 @@ static void close_array(ojParser p) {
 }
 
 static void close_array_class(ojParser p) {
+    VALUE *vp;
     Delegate d = (Delegate)p->ctx;
 
     d->ctail--;
     VALUE *        head = d->vhead + d->ctail->vi + 1;
     volatile VALUE a    = rb_class_new_instance(0, NULL, d->array_class);
 
-    for (VALUE *vp = head; vp < d->vtail; vp++) {
+    for (vp = head; vp < d->vtail; vp++) {
         rb_funcall(a, ltlt_id, 1, *vp);
     }
     d->vtail = head;
@@ -682,6 +686,7 @@ static void mark(ojParser p) {
         return;
     }
     Delegate d = (Delegate)p->ctx;
+    VALUE *vp;
 
     if (NULL == d) {
 	return;
@@ -693,7 +698,7 @@ static void mark(ojParser p) {
     if (NULL != d->class_cache) {
         cache_mark(d->class_cache);
     }
-    for (VALUE *vp = d->vhead; vp < d->vtail; vp++) {
+    for (vp = d->vhead; vp < d->vtail; vp++) {
         if (Qundef != *vp) {
             rb_gc_mark(*vp);
         }
@@ -1091,6 +1096,7 @@ static VALUE opt_symbol_keys_set(ojParser p, VALUE value) {
 }
 
 static VALUE option(ojParser p, const char *key, VALUE value) {
+    struct opt *op;
     struct opt opts[] = {
         {.name = "array_class", .func = opt_array_class},
         {.name = "array_class=", .func = opt_array_class_set},
@@ -1119,7 +1125,7 @@ static VALUE option(ojParser p, const char *key, VALUE value) {
         {.name = NULL},
     };
 
-    for (struct opt *op = opts; NULL != op->name; op++) {
+    for (op = opts; NULL != op->name; op++) {
         if (0 == strcmp(key, op->name)) {
             return op->func(p, value);
         }
diff --git a/ext/oj/validate.c b/ext/oj/validate.c
index 2fd9e15a..a636b6eb 100644
--- a/ext/oj/validate.c
+++ b/ext/oj/validate.c
@@ -28,8 +28,9 @@ mark(ojParser p) {
 void oj_set_parser_validator(ojParser p) {
     p->ctx = NULL;
     Funcs	end = p->funcs + 3;
+    Funcs f;
 
-    for (Funcs f = p->funcs; f < end; f++) {
+    for (f = p->funcs; f < end; f++) {
 	f->add_null = noop;
 	f->add_true = noop;
 	f->add_false = noop;