diff --git a/src/tag/TagPool.cxx b/src/tag/TagPool.cxx
index 2108a98c3..f7e12dd87 100644
--- a/src/tag/TagPool.cxx
+++ b/src/tag/TagPool.cxx
@@ -29,7 +29,7 @@
 
 Mutex tag_pool_lock;
 
-#define NUM_SLOTS 4096
+static constexpr size_t NUM_SLOTS = 4096;
 
 struct TagPoolSlot {
 	TagPoolSlot *next;