diff --git a/repos/base/include/base/heap.h b/repos/base/include/base/heap.h
index 1abd508bdb..0bb7355694 100644
--- a/repos/base/include/base/heap.h
+++ b/repos/base/include/base/heap.h
@@ -119,7 +119,7 @@ class Genode::Heap : public Allocator
 
 	public:
 
-		static constexpr size_t UNLIMITED = ~0;
+		static constexpr size_t UNLIMITED = ~0UL;
 
 		Heap(Ram_allocator *ram_allocator,
 		     Region_map    *region_map,