diff --git a/core/wiki/macros/CSS.tid b/core/wiki/macros/CSS.tid
index 59826452d..44ae8ff64 100644
--- a/core/wiki/macros/CSS.tid
+++ b/core/wiki/macros/CSS.tid
@@ -79,8 +79,12 @@ tags: $:/tags/Macro
 [function[colour],<name>]
 \end color
 
+\function tf.check-colour-contrast-subfunction()
+[function[colour],<paletteEntryA>] [function[colour],<paletteEntryB>] +[colour-contrast:DeltaPhi[]fixed[3]]
+\end tf.check-colour-contrast-subfunction
+
 \function tf.check-colour-contrast(paletteEntryA,paletteEntryB,threshold)
-[function[colour],<paletteEntryA>] [function[colour],<paletteEntryB>] +[colour-contrast:DeltaPhi[]compare:number:gt<threshold>then[ok]] :else[<paletteEntryA>addsuffix[/]addsuffix<paletteEntryB>addsuffix[ contrast is too low]]
+[function[tf.check-colour-contrast-subfunction]compare:number:gt<threshold>then[ok]] :else[function[tf.check-colour-contrast-subfunction]addsuffix[: ]addsuffix<paletteEntryA>addsuffix[/]addsuffix<paletteEntryB>addsuffix[ contrast is too low]]
 \end tf.check-colour-contrast
 
 \define box-shadow(shadow)