diff --git a/src/hnswvacuum.c b/src/hnswvacuum.c
index 8ed56e3..ff18cf1 100644
--- a/src/hnswvacuum.c
+++ b/src/hnswvacuum.c
@@ -1,5 +1,7 @@
 #include "postgres.h"
 
+#include <math.h>
+
 #include "commands/vacuum.h"
 #include "hnsw.h"
 #include "storage/bufmgr.h"