diff --git a/chapters/interface.tex b/chapters/interface.tex
index e1d3f60ef..3de052bb8 100644
--- a/chapters/interface.tex
+++ b/chapters/interface.tex
@@ -585,7 +585,7 @@ \section{Function-Compatibility or Function-Subtyping for Functions}\label{funct
 inside \lstinline!PlanetSimulation! is function-compatible with
 \lstinline!GravityInterface!.
 
-The constant failed in \lstinline!planet1!, will violate variability constraints, whereas it will work in \lstinline!planet2!.
+The constant \lstinline!failed! in \lstinline!planet1!, will violate variability constraints, whereas it will work in \lstinline!planet2!.
 The call \lstinline!gravity(frame_a.r0)! will work in both of them.
 \end{example}