Index: configure.ac
==================================================================
--- configure.ac
+++ configure.ac
@@ -84,11 +84,16 @@
 OBJCFLAGS="$OBJCFLAGS -fconstant-string-class=OFConstantString"
 
 AX_CHECK_COMPILER_FLAGS(-std=c11, [
 	OBJCFLAGS="$OBJCFLAGS -std=c11"
 ], [
-	AX_CHECK_COMPILER_FLAGS(-std=c99, [OBJCFLAGS="$OBJCFLAGS -std=c99"])
+	AX_CHECK_COMPILER_FLAGS(-std=c1x, [
+		OBJCFLAGS="$OBJCFLAGS -std=c1x"
+	], [
+		AX_CHECK_COMPILER_FLAGS(-std=c99,
+			[OBJCFLAGS="$OBJCFLAGS -std=c99"])
+	])
 ])
 
 AX_CHECK_COMPILER_FLAGS(-pipe, [OBJCFLAGS="$OBJCFLAGS -pipe"])
 AX_CHECK_COMPILER_FLAGS(-fno-common, [OBJCFLAGS="$OBJCFLAGS -fno-common"])
 AX_CHECK_COMPILER_FLAGS(-fno-constant-cfstrings, [