diff --git a/redmine/Dockerfile b/redmine/Dockerfile
index add01b35..08268876 100644
--- a/redmine/Dockerfile
+++ b/redmine/Dockerfile
@@ -1,4 +1,4 @@
-FROM redmine:3.4-passenger
+FROM redmine:4.1-passenger
 
 RUN	apt-get update && \
 	apt-get install -y --no-install-recommends \
@@ -12,5 +12,8 @@ RUN	apt-get update && \
 #ADD	hmac.diff /tmp/hmac.diff
 #RUN	cd / && patch -p0 < /tmp/hmac.diff
 
+ADD	openid_server_length_empty.diff /tmp/openid_server_length_empty.diff
+RUN 	cd /usr/local/bundle/gems/ruby-openid-2.9.2 && patch -p1 < /tmp/openid_server_length_empty.diff
+
 ADD	commitlog-references-oshash.diff /tmp/commitlog-references-oshash.diff
 RUN	cd /usr/src/redmine && patch -p1 < /tmp/commitlog-references-oshash.diff
diff --git a/redmine/openid_server_length_empty.diff b/redmine/openid_server_length_empty.diff
new file mode 100644
index 00000000..a15b4449
--- /dev/null
+++ b/redmine/openid_server_length_empty.diff
@@ -0,0 +1,13 @@
+diff --git a/lib/openid/server.rb b/lib/openid/server.rb
+index 8fa1513..3a86e7d 100644
+--- a/lib/openid/server.rb
++++ b/lib/openid/server.rb
+@@ -1240,7 +1240,7 @@ module OpenID
+       # Raises ProtocolError when the query does not seem to be a valid
+       # OpenID request.
+       def decode(query)
+-        if query.nil? or query.length == 0
++        if query.nil? or query.empty? == 0
+           return nil
+         end
+