diff --git a/mozilla/widget/src/mac/nsComboBox.cpp b/mozilla/widget/src/mac/nsComboBox.cpp
index 034f192c7c4..9d74d19a0fa 100644
--- a/mozilla/widget/src/mac/nsComboBox.cpp
+++ b/mozilla/widget/src/mac/nsComboBox.cpp
@@ -291,7 +291,7 @@ PRInt32 nsComboBox::GetSelectedIndex()
 	if (! mMenuHandle)
 		return -1;
 
-	return ::GetControlValue(mControl);
+	return ::GetControlValue(mControl) - 1;
 }
 
 //-------------------------------------------------------------------------