diff --git a/utils/changevalue.c b/utils/changevalue.c
index 5c57b63fef333e4956b9819402afce55a041448f..4b2efd4c48fa0a41ddd100c29b78a8956a847bd6 100644
--- a/utils/changevalue.c
+++ b/utils/changevalue.c
@@ -6,6 +6,8 @@
 #include <math.h>
 #include <assert.h>
 
+double wallclock_time(void);
+
 /*********************** self documentation **********************/
 char *sdoc[] = {
 " ",