diff --git a/src/utils.h b/src/utils.h
index cdc2f14..48363a7 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -1,7 +1,7 @@
 #ifndef UTILS_H
 #define UTILS_H
 
-double normalcdf(double z);
+double normalcdf(double x);
 
 double gaussrand();