diff --git a/crypto/x509/pcy_map.c b/crypto/x509/pcy_map.c
index b599ff9804..d129eca4c3 100644
--- a/crypto/x509/pcy_map.c
+++ b/crypto/x509/pcy_map.c
@@ -73,8 +73,10 @@ int ossl_policy_cache_set_mapping(X509 *x, POLICY_MAPPINGS *maps)
 
     ret = 1;
  bad_mapping:
-    if (ret == -1)
+    if (ret == -1 && CRYPTO_THREAD_write_lock(x->lock)) {
         x->ex_flags |= EXFLAG_INVALID_POLICY;
+        CRYPTO_THREAD_unlock(x->lock);
+    }
     sk_POLICY_MAPPING_pop_free(maps, POLICY_MAPPING_free);
     return ret;