@@ -472,13 +472,10 @@
 objc_allocateClassPair(Class superclass, const char *name, size_t extraBytes)
 {
 	struct objc_class *class, *metaclass;
 	Class iter, rootclass = Nil;
 
-	if (extraBytes > LONG_MAX)
-		OBJC_ERROR("extraBytes out of range!");
-
 	if ((class = calloc(1, sizeof(*class))) == NULL ||
 	    (metaclass = calloc(1, sizeof(*class))) == NULL)
 		OBJC_ERROR("Not enough memory to allocate class pair for class "
 		    "%s!", name);
 
@@ -485,11 +482,17 @@
 	class->isa = metaclass;
 	class->superclass = superclass;
 	class->name = name;
 	class->info = OBJC_CLASS_INFO_CLASS;
 	class->instanceSize = (superclass != Nil ?
-	    superclass->instanceSize : 0) + (long)extraBytes;
+	    superclass->instanceSize : 0);
+
+	if (extraBytes > LONG_MAX ||
+	    LONG_MAX - class->instanceSize < (long)extraBytes)
+		OBJC_ERROR("extraBytes too large!");
+
+	class->instanceSize += (long)extraBytes;
 
 	for (iter = superclass; iter != Nil; iter = iter->superclass)
 		rootclass = iter;
 
 	metaclass->isa = (rootclass != Nil ? rootclass->isa : class);
@@ -629,11 +632,12 @@
 
 	if ((ret = malloc((classesCount + 1) * sizeof(Class))) == NULL)
 		OBJC_ERROR("Failed to allocate memory for class list!");
 
 	count = objc_getClassList(ret, classesCount);
-	OFEnsure(count == classesCount);
+	if (count != classesCount)
+		OBJC_ERROR("Fatal internal inconsistency!");
 
 	ret[count] = Nil;
 
 	if (length != NULL)
 		*length = count;
@@ -978,11 +982,12 @@
 			 */
 			i = UINT32_MAX;
 		}
 	}
 
-	OFEnsure(classesCount == 0);
+	if (classesCount != 0)
+		OBJC_ERROR("Fatal internal inconsistency!");
 
 	if (emptyDTable != NULL) {
 		objc_dtable_free(emptyDTable);
 		emptyDTable = NULL;
 	}