diff --git a/lib/internal/crypto/cfrg.js b/lib/internal/crypto/cfrg.js
index 98e236052f555e..7b825fc93e0669 100644
--- a/lib/internal/crypto/cfrg.js
+++ b/lib/internal/crypto/cfrg.js
@@ -276,6 +276,10 @@ async function cfrgImportKey(
         }
       }
 
+      if (!isPublic && typeof keyData.x !== 'string') {
+        throw lazyDOMException('Invalid JWK keyData', 'DataError');
+      }
+
       verifyAcceptableCfrgKeyUse(
         name,
         isPublic ? 'public' : 'private',