diff --git a/test~coding~readingCppPrograms.fr/docker-compile-and-run b/test~coding~readingCppPrograms.fr/docker-compile-and-run
index 1621a59c3555e72b1241a5f19e79713b10a1bead..a64df2645e004d64f45a18a71b0cf70e47e7bc88 100755
--- a/test~coding~readingCppPrograms.fr/docker-compile-and-run
+++ b/test~coding~readingCppPrograms.fr/docker-compile-and-run
@@ -12,7 +12,7 @@ usage () {
     echo The exit status is that of the compiler.
 }
 
-if [ -n $1 ]; then
+if [ x"$1" = "x" ]; then
     usage
     exit 0
 fi