diff --git a/src/cache.c b/src/cache.c
index 6988b15..35568bc 100644
--- a/src/cache.c
+++ b/src/cache.c
@@ -73,7 +73,7 @@
 };
 
 #define CACHE_BLOCKSIZE 1024
-#define CACHE_ENTRY_MAX_AGE 2147483648
+#define CACHE_ENTRY_MAX_AGE 2147483648U
 
 static struct list caches = LIST_HEAD_INIT(caches);
 static struct cache *tmp_cache_config = NULL;