diff --git a/lib/asn1/check-common.h b/lib/asn1/check-common.h
index 8b772b3d0..b1cb647e6 100644
--- a/lib/asn1/check-common.h
+++ b/lib/asn1/check-common.h
@@ -34,7 +34,7 @@
 struct test_case {
     void *val;
     int byte_len;
-    const unsigned char *bytes;
+    const char *bytes;
     char *name;
 };