diff --git a/.gitignore b/.gitignore
index b2f1825..4ecaa75 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,4 @@
-*.iml
-.idea/*
-*.swp
-target/*
++*.iml
++.idea/*
++*.swp
++target/*
\ No newline at end of file
diff --git a/src/main/java/com/yammer/dropwizard/authenticator/LdapAuthenticator.java b/src/main/java/com/yammer/dropwizard/authenticator/LdapAuthenticator.java
index e1afa7a..9fd9780 100644
--- a/src/main/java/com/yammer/dropwizard/authenticator/LdapAuthenticator.java
+++ b/src/main/java/com/yammer/dropwizard/authenticator/LdapAuthenticator.java
@@ -64,6 +64,9 @@ private boolean filterByGroup(InitialDirContext context, String sanitizedUsernam
     }
 
     private Set<String> getGroupMembershipsIntersectingWithRestrictedGroups(InitialDirContext context, String userName) throws NamingException {
+
+        userName = userNameBaseOnGroupClass(userName);
+
         final String filter = String.format("(&(%s=%s)(objectClass=%s))", configuration.getGroupMembershipAttribute(), userName, configuration.getGroupClassName());
         final NamingEnumeration<SearchResult> result = context.search(configuration.getGroupFilter(), filter, new SearchControls());
 
@@ -84,6 +87,14 @@ private Set<String> getGroupMembershipsIntersectingWithRestrictedGroups(InitialD
         }
     }
 
+    private String userNameBaseOnGroupClass(String userName) {
+        if ("groupOfNames".equalsIgnoreCase(configuration.getGroupClassName())
+                && "member".equalsIgnoreCase(configuration.getGroupMembershipAttribute())) {
+            return toUserDN(userName);
+        }
+        return userName;
+    }
+
     @Timed
     public boolean authenticate(BasicCredentials credentials) throws io.dropwizard.auth.AuthenticationException {
         final String sanitizedUsername = sanitizeEntity(credentials.getUsername());
@@ -101,7 +112,7 @@ public boolean authenticate(BasicCredentials credentials) throws io.dropwizard.a
     }
 
     private AutoclosingDirContext buildContext(String sanitizedUsername, String password) throws NamingException {
-        final String userDN = String.format("%s=%s,%s", configuration.getUserNameAttribute(), sanitizedUsername, configuration.getUserFilter());
+        final String userDN = toUserDN(sanitizedUsername);
 
         final Hashtable<String, String> env = contextConfiguration();
 
@@ -111,6 +122,10 @@ private AutoclosingDirContext buildContext(String sanitizedUsername, String pass
         return new AutoclosingDirContext(env);
     }
 
+    private String toUserDN(String username) {
+        return String.format("%s=%s,%s", configuration.getUserNameAttribute(), username, configuration.getUserFilter());
+    }
+
     @Timed
     public Optional<User> authenticateAndReturnPermittedGroups(BasicCredentials credentials) throws io.dropwizard.auth.AuthenticationException {
         final String sanitizedUsername = sanitizeEntity(credentials.getUsername());
@@ -141,4 +156,4 @@ private Hashtable<String, String> contextConfiguration() {
 
         return env;
     }
-}
+}
\ No newline at end of file