Index: configure.ac
==================================================================
--- configure.ac
+++ configure.ac
@@ -11,10 +11,15 @@
 
 CFLAGS="$CFLAGS -Wall"
 OBJCFLAGS="$OBJCFLAGS -Wall -fobjc-exceptions"
 OBJCFLAGS="$OBJCFLAGS -fconstant-string-class=OFConstString"
 LIBS="$LIBS -lobjc"
+
+if test x"$GCC" = x"yes"; then
+	CFLAGS="$CFLAGS -Werror"
+	OBJCFLAGS="$OBJCFLAGS -Werror"
+fi
 
 AX_CHECK_COMPILER_FLAGS(-pipe, [
 	CFLAGS="$CFLAGS -pipe"
 	OBJCFLAGS="$OBJCFLAGS -pipe"])
 AX_CHECK_COMPILER_FLAGS(-fno-constant-cfstrings,

Index: src/OFConstString.m
==================================================================
--- src/OFConstString.m
+++ src/OFConstString.m
@@ -20,31 +20,22 @@
 #import "OFString.h"
 #import "OFExceptions.h"
 #import "OFMacros.h"
 
 #ifndef __objc_INCLUDE_GNU
-struct objc_class _OFConstStringClassReference;
+void *_OFConstStringClassReference;
 #endif
 
 @implementation OFConstString
 #ifndef __objc_INCLUDE_GNU
 + (void)load
 {
-	Class cls = objc_getClass("OFConstString");
-	memcpy(&_OFConstStringClassReference, cls,
-	    sizeof(_OFConstStringClassReference));
-	objc_addClass(&_OFConstStringClassReference);
+	objc_setFutureClass((Class)&_OFConstStringClassReference,
+	    "OFConstString");
 }
 #endif
 
-- (BOOL)isKindOf: (Class)c
-{
-	if (c == [OFConstString class])
-		return YES;
-	return NO;
-}
-
 - (const char*)cString
 {
 	return string;
 }