diff --git a/extensions/guacamole-auth-ldap/schema/guacConfigGroup.ldif b/extensions/guacamole-auth-ldap/schema/guacConfigGroup.ldif
index 36622e280..f445bc8a5 100644
--- a/extensions/guacamole-auth-ldap/schema/guacConfigGroup.ldif
+++ b/extensions/guacamole-auth-ldap/schema/guacConfigGroup.ldif
@@ -26,6 +26,7 @@ olcAttributeTypes: ( 1.3.6.1.4.1.38971.1.1.1 NAME 'guacConfigProtocol'
 olcAttributeTypes: ( 1.3.6.1.4.1.38971.1.1.2 NAME 'guacConfigParameter'
   SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )
 olcAttributeTypes: ( 1.3.6.1.4.1.38971.1.1.3 NAME 'guacConfigProxyHostname'
+  SINGLE-VALUE
   SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )
 olcAttributeTypes: ( 1.3.6.1.4.1.38971.1.1.4 NAME 'guacConfigProxyPort'
   SINGLE-VALUE
diff --git a/extensions/guacamole-auth-ldap/schema/guacConfigGroup.schema b/extensions/guacamole-auth-ldap/schema/guacConfigGroup.schema
index fb7ec433e..d54d90a3e 100644
--- a/extensions/guacamole-auth-ldap/schema/guacConfigGroup.schema
+++ b/extensions/guacamole-auth-ldap/schema/guacConfigGroup.schema
@@ -24,6 +24,7 @@ attributetype ( 1.3.6.1.4.1.38971.1.1.2 NAME 'guacConfigParameter'
     SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )
 
 attributetype ( 1.3.6.1.4.1.38971.1.1.3 NAME 'guacConfigProxyHostname'
+    SINGLE-VALUE
     SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )
 
 attributetype ( 1.3.6.1.4.1.38971.1.1.4 NAME 'guacConfigProxyPort'