diff --git a/src/ivfkmeans.c b/src/ivfkmeans.c
index cddd724..0079dea 100644
--- a/src/ivfkmeans.c
+++ b/src/ivfkmeans.c
@@ -1,6 +1,7 @@
 #include "postgres.h"
 
 #include <float.h>
+#include <math.h>
 
 #include "ivfflat.h"
 #include "miscadmin.h"