diff --git a/core/plugin.py b/core/plugin.py
index 92127fc..22ab1c4 100644
--- a/core/plugin.py
+++ b/core/plugin.py
@@ -18,8 +18,8 @@ def _recursive_update(d, u):
     # Update value of a nested dictionary of varying depth
 
     for k, v in u.items():
-        if isinstance(d, collections.Mapping):
-            if isinstance(v, collections.Mapping):
+        if isinstance(d, collections.abc.Mapping):
+            if isinstance(v, collections.abc.Mapping):
                 r = _recursive_update(d.get(k, {}), v)
                 d[k] = r
             else:
diff --git a/requirements.txt b/requirements.txt
index 031fa4b..2a8be62 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,4 +4,3 @@ chardet==3.0.4
 idna==2.8
 requests==2.22.0
 urllib3==1.24.1
-wsgiref==0.1.2