diff --git a/tests/unit/unit2604.c b/tests/unit/unit2604.c
index 2657c37f76..e8a9d76a33 100644
--- a/tests/unit/unit2604.c
+++ b/tests/unit/unit2604.c
@@ -75,7 +75,7 @@ static CURLcode test_unit2604(const char *arg)
 #pragma GCC diagnostic pop
 #endif
 
-  char *cp0 = malloc(too_long + 1);
+  char *cp0 = calloc(1, too_long + 1);
   abort_unless(cp0, "could not alloc too long value");
   memset(cp0, 'a', too_long);