diff --git a/internal/impl/decode.go b/internal/impl/decode.go
index a2993d4..6e78faa 100644
--- a/internal/impl/decode.go
+++ b/internal/impl/decode.go
@@ -189,7 +189,7 @@
 			if err == preg.NotFound {
 				return out, errUnknown
 			}
-			return out, err
+			return out, errors.New("%v: unable to resolve extension %v: %v", mi.Desc.FullName(), num, err)
 		}
 	}
 	xi := getExtensionFieldInfo(xt)