diff --git a/ChangeLog b/ChangeLog
index 9c0b202..35aecdd 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2010-11-11 Richard Frith-Macdonald  <rfm@gnu.org>
+
+	* GSCache.m: Try to get defines right to get instance size depending
+	on the runtime in use.
+
 2010-11-10 Riccardo Mottola
 
 	* GSLinkedList.h
diff --git a/GSCache.m b/GSCache.m
index cbbb4e3..38456ed 100644
--- a/GSCache.m
+++ b/GSCache.m
@@ -757,10 +757,10 @@ static void removeItem(GSCacheItem *item, GSCacheItem **first)
       return 0;
     }
   [exclude addObject: self];
-#if !defined(GNUSTEP)
+#if defined(__OBJC2__) || defined(GNUSTEP)
   return class_getInstanceSize(isa);
 #else
-  return isa->instance_size;
+  return ((struct objc_class *)isa)->instance_size;
 #endif
 }
 @end