diff --git a/lib/krb5/crypto.c b/lib/krb5/crypto.c
index bdcdb2ea0..68233c290 100644
--- a/lib/krb5/crypto.c
+++ b/lib/krb5/crypto.c
@@ -2058,7 +2058,7 @@ evp_encrypt(krb5_context context,
     return 0;
 }
 
-static const char zero_ivec[EVP_MAX_BLOCK_LENGTH] = { 0 };
+static const unsigned char zero_ivec[EVP_MAX_BLOCK_LENGTH] = { 0 };
 
 static krb5_error_code
 evp_encrypt_cts(krb5_context context,