diff --git a/CMakeLists.txt b/CMakeLists.txt
index c17239b..9bb5314 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -8,6 +8,7 @@ cmake_minimum_required(VERSION 2.6)
 
 option(USE_INTERNAL_FPCONV "Use internal strtod() / g_fmt() code for performance")
 option(MULTIPLE_THREADS "Support multi-threaded apps with internal fpconv - recommended" ON)
+option(USE_ECMA_262 "Use ecma-262 formatting rules for internal g_fmt()")
 
 if(NOT CMAKE_BUILD_TYPE)
     set(CMAKE_BUILD_TYPE Release CACHE STRING
@@ -18,6 +19,10 @@ endif()
 find_package(Lua51 REQUIRED)
 include_directories(${LUA_INCLUDE_DIR})
 
+if(USE_ECMA_262)
+    add_definitions(-DUSE_ECMA_262)
+endif()
+
 if(NOT USE_INTERNAL_FPCONV)
     # Use libc number conversion routines (strtod(), sprintf())
     set(FPCONV_SOURCES fpconv.c)
diff --git a/Makefile b/Makefile
index 2361028..35d4d20 100644
--- a/Makefile
+++ b/Makefile
@@ -60,6 +60,10 @@ FPCONV_OBJS =       fpconv.o
 #FPCONV_OBJS =       g_fmt.o dtoa.o
 #CJSON_CFLAGS +=     -DUSE_INTERNAL_FPCONV
 
+## Use ecma-262 formatting rules for internal number conversion
+#FPCONV_OBJS =       g_fmt.o dtoa.o
+#CJSON_CFLAGS +=     -DUSE_INTERNAL_FPCONV -DUSE_ECMA_262
+
 ## Compile built in number conversion for big endian architectures
 #CJSON_CFLAGS +=     -DIEEE_BIG_ENDIAN
 
diff --git a/g_fmt.c b/g_fmt.c
index 50d6a1d..fcfc9f8 100644
--- a/g_fmt.c
+++ b/g_fmt.c
@@ -58,7 +58,11 @@ fpconv_g_fmt(char *b, double x, int precision)
 		b--;
 		goto done0;
 		}
+#ifdef USE_ECMA_262
+	if (decpt <= -6 || decpt > 21) {
+#else
 	if (decpt <= -4 || decpt > precision) {
+#endif
 		*b++ = *s++;
 		if (*s) {
 			*b++ = '.';
@@ -106,6 +110,13 @@ fpconv_g_fmt(char *b, double x, int precision)
 	freedtoa(s0);
 #ifdef IGNORE_ZERO_SIGN
  done:
+#endif
+#ifdef USE_ECMA_262
+	int len = b - b0;
+	if (len >= 4 && b0[len - 4] == 'e' && b0[len-3] == '-' && b0[len-2] == '0') {
+		b0[len-2] = b0[len - 1];
+		*--b = 0;
+	}
 #endif
 	return b - b0;
 	}