diff --git a/my-listings.sty b/my-listings.sty
index cb5dc30ab866c30e4163e229b4b15d1feaf79a4a..ea0e8781d8cbcf894c664f9db4bc55eef6f3c1bf 100644
--- a/my-listings.sty
+++ b/my-listings.sty
@@ -86,7 +86,7 @@
 }
 
 \lstdefinelanguage{PrologInt}{
-  morekeywords={Redo, Call, Fatal, Error, error},
+  morekeywords={Redo, Call, Fatal, Error, error, ERROR, yes, no, true, false},
   keywordstyle=\color{black}\bfseries,
   stringstyle=\color{black},
   commentstyle=\color{black},