diff --git a/src/ivfflat.h b/src/ivfflat.h
index 21a9f08..5d8535c 100644
--- a/src/ivfflat.h
+++ b/src/ivfflat.h
@@ -56,7 +56,7 @@
 		(code); \
 		INSTR_TIME_SET_CURRENT(duration); \
 		INSTR_TIME_SUBTRACT(duration, start); \
-		elog(INFO, "%s: %f ms", name, INSTR_TIME_GET_MILLISEC(duration)); \
+		elog(INFO, "%s: %.3f ms", name, INSTR_TIME_GET_MILLISEC(duration)); \
 	} while (0)
 #else
 #define Bench(name, code) (code)