diff --git a/SCons/Config/gnu b/SCons/Config/gnu
index 3f31138f..99b9f12c 100644
--- a/SCons/Config/gnu
+++ b/SCons/Config/gnu
@@ -210,6 +210,36 @@ if conf.CheckPThread():
 	makensis_env.Append(LINKFLAGS = '-pthread')
 conf.Finish()
 
+#
+# GCC doesn't define __BIG_ENDIAN__ or __LITTLE_ENDIAN__, so manually check
+# for the endianess and define __BIG_ENDIAN__ if needed.
+#
+
+def check_big_endian(ctx):
+	ctx.Message('Checking for __BIG_ENDIAN__... ')
+
+	test = """
+		int main() {
+			#ifdef __BIG_ENDIAN__
+				// already defined, no need to define again
+				return 0;
+			#else
+				int i = 1;
+				char *c = (char *) &i;
+				return c[0] != 1;
+			#endif
+		}
+	"""
+
+	result = not ctx.TryRun(test, '.c')[0]
+	ctx.Result(result)
+	return result
+
+conf = defenv.Configure(custom_tests = { 'CheckBigEndian' : check_big_endian })
+if conf.CheckBigEndian():
+	makensis_env.Append(CPPFLAGS = ['__BIG_ENDIAN__'])
+conf.Finish()
+
 ### return
 
 Return('stub_env makensis_env plugin_env util_env cp_util_env')