Index: configure.ac
==================================================================
--- configure.ac
+++ configure.ac
@@ -164,12 +164,18 @@
 		], [
 			AC_MSG_ERROR([libobjc not found!])
 		])
 		;;
 	GNU)
-		AC_DEFINE(OF_GNU_RUNTIME, 1,
-			[Whether we use the GNU ObjC runtime])
+		# The new API of the new GNU runtime is currently too broken to
+		# be of any use, thus we even use the old API when the new one
+		# is detected until the new one has been fixed and offers a way
+		# to detect if it is the fixed one.
+		dnl AC_DEFINE(OF_GNU_RUNTIME, 1,
+		dnl	[Whether we use the GNU ObjC runtime])
+		AC_DEFINE(OF_OLD_GNU_RUNTIME, 1,
+			[Whether we use the old GNU ObjC runtime])
 
 		AC_CHECK_LIB(objc, objc_msg_lookup, [
 			LIBS="-lobjc $LIBS"
 		], [
 			AC_MSG_ERROR([libobjc not found!])

Index: src/OFObject.m
==================================================================
--- src/OFObject.m
+++ src/OFObject.m
@@ -107,10 +107,14 @@
 objc_enumerationMutation(id object)
 {
 	enumeration_mutation_handler(object);
 }
 #endif
+
+#if defined(HAVE_OBJC_ENUMERATIONMUTATION) && defined(OF_OLD_GNU_RUNTIME)
+extern void objc_setEnumerationMutationHandler(void(*handler)(id));
+#endif
 
 const char*
 _NSPrintForDebugger(id object)
 {
 	return [[object description] cString];
@@ -170,11 +174,11 @@
 		    stderr);
 		abort();
 	}
 #endif
 
-#if defined(OF_APPLE_RUNTIME) || defined(OF_GNU_RUNTIME)
+#ifdef HAVE_OBJC_ENUMERATIONMUTATION
 	objc_setEnumerationMutationHandler(enumeration_mutation_handler);
 #endif
 
 	cxx_construct = sel_registerName(".cxx_construct");
 	cxx_destruct = sel_registerName(".cxx_destruct");