diff --git a/ext/rapidjson/cext.cc b/ext/rapidjson/cext.cc
index 10478a8..c97e549 100644
--- a/ext/rapidjson/cext.cc
+++ b/ext/rapidjson/cext.cc
@@ -8,6 +8,8 @@ static VALUE rb_mRapidJSON;
 static VALUE rb_eParseError;
 static VALUE rb_eEncodeError;
 
+static VALUE rb_LLONG_MIN = Qnil, rb_ULLONG_MAX = Qnil;
+
 static ID id_to_json;
 static ID id_to_s;
 
@@ -36,7 +38,8 @@ parse(VALUE _self, VALUE string) {
     Reader reader;
     char *cstring = StringValueCStr(string); // fixme?
     StringStream ss(cstring);
-    ParseResult ok = reader.Parse(ss, handler);
+    // TODO: rapidjson::kParseInsituFlag ?
+    ParseResult ok = reader.Parse<rapidjson::kParseNumbersAsStringsFlag>(ss, handler);
 
     if (!ok) {
         rb_raise(rb_eParseError, "JSON parse error: %s (%lu)",
@@ -67,6 +70,12 @@ Init_rapidjson(void)
     id_to_s = rb_intern("to_s");
     id_to_json = rb_intern("to_json");
 
+    rb_global_variable(&rb_LLONG_MIN);
+    rb_global_variable(&rb_ULLONG_MAX);
+
+    rb_LLONG_MIN = LL2NUM(LLONG_MIN);
+    rb_ULLONG_MAX = ULL2NUM(ULLONG_MAX);
+
     rb_mRapidJSON = rb_define_module("RapidJSON");
     rb_define_module_function(rb_mRapidJSON, "encode", encode, 1);
     rb_define_module_function(rb_mRapidJSON, "pretty_encode", pretty_encode, 1);
diff --git a/ext/rapidjson/encoder.hh b/ext/rapidjson/encoder.hh
index 53cd592..b5f0f78 100644
--- a/ext/rapidjson/encoder.hh
+++ b/ext/rapidjson/encoder.hh
@@ -67,12 +67,24 @@ class RubyObjectEncoder {
 
         bool negative = rb_big_cmp(b, INT2FIX(0)) == INT2FIX(-1);
         if (negative) {
-            long long ll = rb_big2ll(b);
-            writer.Int64(ll);
-        } else {
+            if (rb_big_cmp(b, rb_LLONG_MIN) != INT2FIX(-1)) {
+                long long ll = rb_big2ll(b);
+                writer.Int64(ll);
+                return;
+            }
+        } else if (rb_big_cmp(b, rb_ULLONG_MAX) == INT2FIX(-1)) {
             unsigned long long ull = rb_big2ull(b);
             writer.Uint64(ull);
+            return;
         }
+
+        // If the number is too big, we go through Integer#to_s
+        VALUE str = rb_funcall(b, id_to_s, 0);
+        Check_Type(str, T_STRING);
+
+        // We should be able to use RawNumber here, but it's buggy
+        // https://github.com/Tencent/rapidjson/issues/852
+        writer.RawValue(RSTRING_PTR(str), RSTRING_LEN(str), kNumberType);
     }
 
     void encode_float(VALUE v) {
diff --git a/ext/rapidjson/parser.hh b/ext/rapidjson/parser.hh
index 9a17894..b9c4a73 100644
--- a/ext/rapidjson/parser.hh
+++ b/ext/rapidjson/parser.hh
@@ -33,20 +33,23 @@ struct RubyObjectHandler : public BaseReaderHandler<UTF8<>, RubyObjectHandler> {
         return PutValue(b ? Qtrue : Qfalse);
     }
 
-    bool Int(int i) {
-        return PutValue(INT2FIX(i));
-    }
-
-    bool Uint(unsigned u) {
-        return PutValue(INT2FIX(u));
-    }
-
-    bool Int64(int64_t i) {
-        return PutValue(RB_LONG2NUM(i));
-    }
+    bool RawNumber(const char *str, SizeType length, bool copy) {
+        // TODO: rapidjson::kParseInsituFlag ?
+        // char tmp_string[length + 1];
+        // memcpy(tmp_string, str, length);
+        // tmp_string[length] = '\0';
+
+        SizeType index = 0;
+        if (str[0] == '-') {
+            index++;
+        }
+        for (; index < length; index++) {
+            if (!isdigit(str[index])) {
+                return Double(rb_cstr_to_dbl(str, false));
+            }
+        }
 
-    bool Uint64(uint64_t u) {
-        return PutValue(RB_ULONG2NUM(u));
+        return PutValue(rb_cstr2inum(str, 10));
     }
 
     bool Double(double d) {
diff --git a/test/test_encoder.rb b/test/test_encoder.rb
index 60cfe6a..75b8a8f 100644
--- a/test/test_encoder.rb
+++ b/test/test_encoder.rb
@@ -33,6 +33,10 @@ def test_encode_bignum
     assert_equal "18446744073709551615", encode(2**64 - 1)
   end
 
+  def test_encore_arbitrary_size_num
+    assert_equal "340282366920938463463374607431768211456", encode(2**128)
+  end
+
   def test_encode_fixnum_exponents
     tests = []
     0.upto(65) do |exponent|
diff --git a/test/test_parser.rb b/test/test_parser.rb
index fab2bfa..ea28083 100644
--- a/test/test_parser.rb
+++ b/test/test_parser.rb
@@ -59,6 +59,15 @@ def test_parse_string
     assert_equal "abcdefghijklmnopqrstuvwxyz", parse('"abcdefghijklmnopqrstuvwxyz"')
   end
 
+  def test_parse_bignum
+    assert_equal 340282366920938463463374607431768211456, parse("340282366920938463463374607431768211456")
+  end
+
+  def test_parse_huge_floats
+    assert_equal 34028236692093846.3463374607431768211456, parse("34028236692093846.3463374607431768211456")
+    assert_equal 0.0, parse("123.456e-789")
+  end
+
   def test_parse_invalida
     ex = assert_raises RapidJSON::ParseError do
       parse("abc")