diff --git a/tests/Test_overflow.c b/tests/Test_overflow.c
index b276b6d..8cfe098 100644
--- a/tests/Test_overflow.c
+++ b/tests/Test_overflow.c
@@ -60,7 +60,7 @@ main (int argc, char **argv)
      rejected.  This limitation was introduced with libtasn1 2.12. */
   if (LONG_MAX > INT_MAX)
     {
-      unsigned long num = ((long) UINT_MAX) << 2;
+      unsigned long num = ((unsigned long) UINT_MAX) << 2;
       unsigned char der[20];
       int der_len;
       long l;