diff --git a/ext/json/ext/generator/generator.c b/ext/json/ext/generator/generator.c
index 2a3db296..8cc0c270 100644
--- a/ext/json/ext/generator/generator.c
+++ b/ext/json/ext/generator/generator.c
@@ -7,7 +7,13 @@ static ID i_encoding, i_encode;
 #endif
 
 static VALUE mJSON, mExt, mGenerator, cState, mGeneratorMethods, mObject,
-             mHash, mArray, mFixnum, mBignum, mFloat, mString, mString_Extend,
+             mHash, mArray,
+#ifdef RUBY_INTEGER_UNIFICATION
+             mInteger,
+#else
+             mFixnum, mBignum,
+#endif
+             mFloat, mString, mString_Extend,
              mTrueClass, mFalseClass, mNilClass, eGeneratorError,
              eNestingError, CRegexp_MULTILINE, CJSON_SAFE_STATE_PROTOTYPE,
              i_SAFE_STATE_PROTOTYPE;
@@ -342,6 +348,18 @@ static VALUE mArray_to_json(int argc, VALUE *argv, VALUE self) {
     GENERATE_JSON(array);
 }
 
+#ifdef RUBY_INTEGER_UNIFICATION
+/*
+ * call-seq: to_json(*)
+ *
+ * Returns a JSON string representation for this Integer number.
+ */
+static VALUE mInteger_to_json(int argc, VALUE *argv, VALUE self)
+{
+    GENERATE_JSON(integer);
+}
+
+#else
 /*
  * call-seq: to_json(*)
  *
@@ -361,6 +379,7 @@ static VALUE mBignum_to_json(int argc, VALUE *argv, VALUE self)
 {
     GENERATE_JSON(bignum);
 }
+#endif
 
 /*
  * call-seq: to_json(*)
@@ -822,6 +841,15 @@ static void generate_json_bignum(FBuffer *buffer, VALUE Vstate, JSON_Generator_S
     fbuffer_append_str(buffer, tmp);
 }
 
+#ifdef RUBY_INTEGER_UNIFICATION
+static void generate_json_integer(FBuffer *buffer, VALUE Vstate, JSON_Generator_State *state, VALUE obj)
+{
+    if (FIXNUM_P(obj))
+        generate_json_fixnum(buffer, Vstate, state, obj);
+    else
+        generate_json_bignum(buffer, Vstate, state, obj);
+}
+#endif
 static void generate_json_float(FBuffer *buffer, VALUE Vstate, JSON_Generator_State *state, VALUE obj)
 {
     double value = RFLOAT_VALUE(obj);
@@ -855,9 +883,9 @@ static void generate_json(FBuffer *buffer, VALUE Vstate, JSON_Generator_State *s
         generate_json_false(buffer, Vstate, state, obj);
     } else if (obj == Qtrue) {
         generate_json_true(buffer, Vstate, state, obj);
-    } else if (klass == rb_cFixnum) {
+    } else if (FIXNUM_P(obj)) {
         generate_json_fixnum(buffer, Vstate, state, obj);
-    } else if (klass == rb_cBignum) {
+    } else if (RB_TYPE_P(obj, T_BIGNUM)) {
         generate_json_bignum(buffer, Vstate, state, obj);
     } else if (klass == rb_cFloat) {
         generate_json_float(buffer, Vstate, state, obj);
@@ -1353,10 +1381,15 @@ void Init_generator(void)
     rb_define_method(mHash, "to_json", mHash_to_json, -1);
     mArray = rb_define_module_under(mGeneratorMethods, "Array");
     rb_define_method(mArray, "to_json", mArray_to_json, -1);
+#ifdef RUBY_INTEGER_UNIFICATION
+    mInteger = rb_define_module_under(mGeneratorMethods, "Integer");
+    rb_define_method(mInteger, "to_json", mInteger_to_json, -1);
+#else
     mFixnum = rb_define_module_under(mGeneratorMethods, "Fixnum");
     rb_define_method(mFixnum, "to_json", mFixnum_to_json, -1);
     mBignum = rb_define_module_under(mGeneratorMethods, "Bignum");
     rb_define_method(mBignum, "to_json", mBignum_to_json, -1);
+#endif
     mFloat = rb_define_module_under(mGeneratorMethods, "Float");
     rb_define_method(mFloat, "to_json", mFloat_to_json, -1);
     mString = rb_define_module_under(mGeneratorMethods, "String");
diff --git a/ext/json/ext/generator/generator.h b/ext/json/ext/generator/generator.h
index 7432f268..900b4d58 100644
--- a/ext/json/ext/generator/generator.h
+++ b/ext/json/ext/generator/generator.h
@@ -98,8 +98,12 @@ typedef struct JSON_Generator_StateStruct {
 
 static VALUE mHash_to_json(int argc, VALUE *argv, VALUE self);
 static VALUE mArray_to_json(int argc, VALUE *argv, VALUE self);
+#ifdef RUBY_INTEGER_UNIFICATION
+static VALUE mInteger_to_json(int argc, VALUE *argv, VALUE self);
+#else
 static VALUE mFixnum_to_json(int argc, VALUE *argv, VALUE self);
 static VALUE mBignum_to_json(int argc, VALUE *argv, VALUE self);
+#endif
 static VALUE mFloat_to_json(int argc, VALUE *argv, VALUE self);
 static VALUE mString_included_s(VALUE self, VALUE modul);
 static VALUE mString_to_json(int argc, VALUE *argv, VALUE self);
@@ -121,6 +125,9 @@ static void generate_json_string(FBuffer *buffer, VALUE Vstate, JSON_Generator_S
 static void generate_json_null(FBuffer *buffer, VALUE Vstate, JSON_Generator_State *state, VALUE obj);
 static void generate_json_false(FBuffer *buffer, VALUE Vstate, JSON_Generator_State *state, VALUE obj);
 static void generate_json_true(FBuffer *buffer, VALUE Vstate, JSON_Generator_State *state, VALUE obj);
+#ifdef RUBY_INTEGER_UNIFICATION
+static void generate_json_integer(FBuffer *buffer, VALUE Vstate, JSON_Generator_State *state, VALUE obj);
+#endif
 static void generate_json_fixnum(FBuffer *buffer, VALUE Vstate, JSON_Generator_State *state, VALUE obj);
 static void generate_json_bignum(FBuffer *buffer, VALUE Vstate, JSON_Generator_State *state, VALUE obj);
 static void generate_json_float(FBuffer *buffer, VALUE Vstate, JSON_Generator_State *state, VALUE obj);