diff --git a/tools/conf.yaml b/tools/conf.yaml
index 5da6e70..b334253 100644
--- a/tools/conf.yaml
+++ b/tools/conf.yaml
@@ -21,8 +21,3 @@ registry:
   storage:
     driver: filesystem
     root: /tmp/storage
-  # Check the size of layers matches the size specified in the
-  # container manifest.  Some versions of docker can push invalid
-  # manifests (and *also* don't care about a size mismatch when
-  # pulling); set this to false to ignore layer-size mismatches.
-  strict: true
diff --git a/zuul_registry/main.py b/zuul_registry/main.py
index ccb324d..aa936ab 100644
--- a/zuul_registry/main.py
+++ b/zuul_registry/main.py
@@ -323,38 +323,23 @@ class RegistryAPI:
             data['config']['size'] = size
             changed = True
 
+        # Validate layer sizes
         for layer in data['layers']:
             digest = layer['digest']
             actual_size = self.storage.blob_size(namespace, digest)
-
-            # As above, we may or may not have a size for layers.  If
-            # this layer doesn't have a size, add it.
             if 'size' not in layer:
-                layer['size'] = actual_size
-                changed = True
-                continue
-
-            # However, if we got a size, we validate it
+                msg = ('Client push error: layer %s missing size ' % digest)
+                raise cherrypy.HTTPError(400, msg)
             size = layer['size']
             if size == actual_size:
                 continue
-
             msg = ("Manifest has invalid size for layer %s "
                    "(size:%d actual:%d)" % (digest, size, actual_size))
             self.log.error(msg)
-            # Docker pushes a manifest with sizes one byte larger
-            # than it actaully sends.  We choose to ignore this.
-            #  https://github.com/docker/for-linux/issues/1296
-            if ('docker/' in request.headers.get('User-Agent', '')
-                and (actual_size + 1 == size)):
-                self.log.info("Fix docker layer size for %s" % digest)
-                layer['size'] = actual_size
-                changed = True
-            elif self.conf.get('strict', True):
-                # We don't delete layers here as they may be used by
-                # different images with valid manifests. Return an error to
-                # the client so it can try again.
-                raise cherrypy.HTTPError(400, msg)
+            # We don't delete layers here as they may be used by
+            # different images with valid manifests. Return an error to
+            # the client so it can try again.
+            raise cherrypy.HTTPError(400, msg)
 
         if changed:
             body = json.dumps(data).encode('utf8')