diff --git a/lib/yaml/__init__.py b/lib/yaml/__init__.py
index e7a419dd..9f84c388 100644
--- a/lib/yaml/__init__.py
+++ b/lib/yaml/__init__.py
@@ -329,22 +329,32 @@ def add_path_resolver(tag, path, kind=None, Loader=Loader, Dumper=Dumper):
     Loader.add_path_resolver(tag, path, kind)
     Dumper.add_path_resolver(tag, path, kind)
 
-def add_constructor(tag, constructor, Loader=Loader):
+def add_constructor(tag, constructor, Loader=None):
     """
     Add a constructor for the given tag.
     Constructor is a function that accepts a Loader instance
     and a node object and produces the corresponding Python object.
     """
-    Loader.add_constructor(tag, constructor)
+    if Loader == None:
+        loader.Loader.add_constructor(tag, constructor)
+        loader.FullLoader.add_constructor(tag, constructor)
+        loader.UnsafeLoader.add_constructor(tag, constructor)
+    else:
+        Loader.add_constructor(tag, constructor)
 
-def add_multi_constructor(tag_prefix, multi_constructor, Loader=Loader):
+def add_multi_constructor(tag_prefix, multi_constructor, Loader=None):
     """
     Add a multi-constructor for the given tag prefix.
     Multi-constructor is called for a node if its tag starts with tag_prefix.
     Multi-constructor accepts a Loader instance, a tag suffix,
     and a node object and produces the corresponding Python object.
     """
-    Loader.add_multi_constructor(tag_prefix, multi_constructor)
+    if Loader == None:
+        loader.Loader.add_multi_constructor(tag_prefix, multi_constructor)
+        loader.FullLoader.add_multi_constructor(tag_prefix, multi_constructor)
+        loader.UnsafeLoader.add_multi_constructor(tag_prefix, multi_constructor)
+    else:
+        Loader.add_multi_constructor(tag_prefix, multi_constructor)
 
 def add_representer(data_type, representer, Dumper=Dumper):
     """
diff --git a/lib3/yaml/__init__.py b/lib3/yaml/__init__.py
index 5df0bb5f..a55206ba 100644
--- a/lib3/yaml/__init__.py
+++ b/lib3/yaml/__init__.py
@@ -326,22 +326,32 @@ def add_path_resolver(tag, path, kind=None, Loader=Loader, Dumper=Dumper):
     Loader.add_path_resolver(tag, path, kind)
     Dumper.add_path_resolver(tag, path, kind)
 
-def add_constructor(tag, constructor, Loader=Loader):
+def add_constructor(tag, constructor, Loader=None):
     """
     Add a constructor for the given tag.
     Constructor is a function that accepts a Loader instance
     and a node object and produces the corresponding Python object.
     """
-    Loader.add_constructor(tag, constructor)
+    if Loader == None:
+        loader.Loader.add_constructor(tag, constructor)
+        loader.FullLoader.add_constructor(tag, constructor)
+        loader.UnsafeLoader.add_constructor(tag, constructor)
+    else:
+        Loader.add_constructor(tag, constructor)
 
-def add_multi_constructor(tag_prefix, multi_constructor, Loader=Loader):
+def add_multi_constructor(tag_prefix, multi_constructor, Loader=None):
     """
     Add a multi-constructor for the given tag prefix.
     Multi-constructor is called for a node if its tag starts with tag_prefix.
     Multi-constructor accepts a Loader instance, a tag suffix,
     and a node object and produces the corresponding Python object.
     """
-    Loader.add_multi_constructor(tag_prefix, multi_constructor)
+    if Loader == None:
+        loader.Loader.add_multi_constructor(tag_prefix, multi_constructor)
+        loader.FullLoader.add_multi_constructor(tag_prefix, multi_constructor)
+        loader.UnsafeLoader.add_multi_constructor(tag_prefix, multi_constructor)
+    else:
+        Loader.add_multi_constructor(tag_prefix, multi_constructor)
 
 def add_representer(data_type, representer, Dumper=Dumper):
     """