diff --git a/Contrib/Modern UI/System.nsh b/Contrib/Modern UI/System.nsh
index db801ef7..0b04eb42 100644
--- a/Contrib/Modern UI/System.nsh	
+++ b/Contrib/Modern UI/System.nsh	
@@ -148,10 +148,14 @@ Var MUI_TEMP2
 
   !ifdef MUI_PAGE_HEADER_TEXT & MUI_PAGE_HEADER_SUBTEXT
     !insertmacro MUI_HEADER_TEXT "${MUI_PAGE_HEADER_TEXT}" "${MUI_PAGE_HEADER_SUBTEXT}"
+    !undef MUI_PAGE_HEADER_TEXT
+    !undef MUI_PAGE_HEADER_SUBTEXT
   !else ifdef MUI_PAGE_HEADER_TEXT
     !insertmacro MUI_HEADER_TEXT "${MUI_PAGE_HEADER_TEXT}" "${SUBTEXT}"
+    !undef MUI_PAGE_HEADER_TEXT
   !else ifdef MUI_PAGE_HEADER_SUBTEXT
     !insertmacro MUI_HEADER_TEXT "${TEXT}" "${MUI_PAGE_HEADER_SUBTEXT}"
+    !undef MUI_PAGE_HEADER_SUBTEXT
   !else
     !insertmacro MUI_HEADER_TEXT "${TEXT}" "${SUBTEXT}"
   !endif