diff --git a/ext/opcache/shared_alloc_mmap.c b/ext/opcache/shared_alloc_mmap.c
index 389c79114ab..6627633694f 100644
--- a/ext/opcache/shared_alloc_mmap.c
+++ b/ext/opcache/shared_alloc_mmap.c
@@ -50,7 +50,7 @@ static int create_segments(size_t requested_size, zend_shared_segment ***shared_
 #endif
 #ifdef VM_MAKE_TAG
 	/* allows tracking segments via tools such as vmmap */
-	fd = VM_MAKE_TAG(251);
+	fd = VM_MAKE_TAG(251U);
 #endif
 #ifdef MAP_HUGETLB
 	size_t huge_page_size = 2 * 1024 * 1024;