--- contrib/mod_tls.c
+++ contrib/mod_tls.c
@@ -4383,6 +4383,9 @@ static int tls_verify_crl(int ok, X509_S
       ASN1_INTEGER *sn;
 
       revoked = sk_X509_REVOKED_value(X509_CRL_get_REVOKED(crl), i);
+      if (revoked == NULL) {
+        continue;
+      }
       sn = revoked->serialNumber;
 
       if (ASN1_INTEGER_cmp(sn, X509_get_serialNumber(xs)) == 0) {