diff --git a/blocks_runtime.m b/blocks_runtime.m
index 8290ac1..070fd07 100644
--- a/blocks_runtime.m
+++ b/blocks_runtime.m
@@ -114,7 +114,7 @@ void _Block_object_assign(void *destAddr, const void *object, const int flags)
 				{
 					(*dst)->forwarding = *dst;
 				}
-				if(src->size >= sizeof(struct psy_block_byref_obj))
+				if((size_t)src->size >= sizeof(struct psy_block_byref_obj))
 				{
 					src->byref_keep(*dst, src);
 				}
@@ -161,7 +161,7 @@ void _Block_object_dispose(const void *object, const int flags)
 			src->flags--;
 			if((src->flags & ~BLOCK_HAS_COPY_DISPOSE) == 0)
 			{
-				if(src->size >= sizeof(struct psy_block_byref_obj))
+				if((size_t)src->size >= sizeof(struct psy_block_byref_obj))
 					src->byref_dispose(src);
 				
 				free(src);
diff --git a/class.h b/class.h
index 6d005d3..8a0d726 100644
--- a/class.h
+++ b/class.h
@@ -157,17 +157,17 @@ enum objc_class_flags
 static inline void objc_set_class_flag(struct objc_class *aClass,
                                        enum objc_class_flags flag)
 {
-	aClass->info |= (long)flag;
+	aClass->info |= (unsigned long)flag;
 }
 static inline void objc_clear_class_flag(struct objc_class *aClass,
                                          enum objc_class_flags flag)
 {
-	aClass->info &= ~(long)flag;
+	aClass->info &= ~(unsigned long)flag;
 }
 static inline BOOL objc_test_class_flag(struct objc_class *aClass,
                                         enum objc_class_flags flag)
 {
-	return (aClass->info & (long)flag) == (long)flag;
+	return (aClass->info & (unsigned long)flag) == (unsigned long)flag;
 }
 
 /**