diff --git a/CHANGES/1401.misc.rst b/CHANGES/1401.misc.rst
new file mode 100644
index 00000000..96670eb9
--- /dev/null
+++ b/CHANGES/1401.misc.rst
@@ -0,0 +1 @@
+Improved performance of passing a `dict` or `str` to :py:meth:`~yarl.URL.extend_query` -- by :user:`bdraco`.
diff --git a/yarl/_query.py b/yarl/_query.py
index 65420356..6a663fc9 100644
--- a/yarl/_query.py
+++ b/yarl/_query.py
@@ -97,10 +97,12 @@ def get_str_query(*args: Any, **kwargs: Any) -> Union[str, None]:
         return None
     if not query:
         return ""
-    if isinstance(query, Mapping):
+    if type(query) is dict:
         return get_str_query_from_sequence_iterable(query.items())
-    if isinstance(query, str):
+    if type(query) is str or isinstance(query, str):
         return QUERY_QUOTER(query)
+    if isinstance(query, Mapping):
+        return get_str_query_from_sequence_iterable(query.items())
     if isinstance(query, (bytes, bytearray, memoryview)):
         msg = "Invalid query type: bytes, bytearray and memoryview are forbidden"
         raise TypeError(msg)