diff --git a/indra/llui/llui.h b/indra/llui/llui.h
index 9f6fccfef657fa8d500aeda60d9d8445a1c86fd7..8cec1a16f406170e4a176f06b474552e888fac5e 100644
--- a/indra/llui/llui.h
+++ b/indra/llui/llui.h
@@ -158,8 +158,8 @@ class LLUI
 
 		struct Params : public LLInitParam::Block<Params>
 		{
-			Optional<T>	minimum,
-						maximum;
+			typename Optional<T>	minimum,
+									maximum;
 
 			Params()
 			:	minimum("min", 0),