diff --git a/releng.control/cleanupArtifacts.sh b/releng.control/cleanupArtifacts.sh
index cd0ee53bd77c5ba5a8a7ac5f530847164c6904bc..b50dc862a8f6c58a7771f18066f94c0f226963da 100644
--- a/releng.control/cleanupArtifacts.sh
+++ b/releng.control/cleanupArtifacts.sh
@@ -60,7 +60,7 @@ else
 fi
 
 echo;
-echo "    Removing directories older than " $( ${ndays} + 1 ) " days";
+echo "    Removing directories older than " $(( ${ndays} + 1 )) " days";
 echo "        (from under ${parentDir})";
 before=`find ${parentDir} -mindepth 2 -maxdepth 2 | wc -l`;
 echo "            number of directories before cleaning: ${before}";
@@ -102,7 +102,7 @@ fi
 
 
 echo;
-echo "    Removing directories older  than " $( ${ndays} + 1 ) " days";
+echo "    Removing directories older  than " $(( ${ndays} + 1 )) " days";
 echo "        (from under ${parentDir})";
 before=`find ${parentDir} -mindepth 1 -maxdepth 1 | wc -l`;
 echo "            number of directories before cleaning: ${before}";
@@ -146,7 +146,7 @@ fi
 
 
 echo;
-echo "    Removing directories and files older  than " $( ${ndays} + 1 ) " days";
+echo "    Removing directories and files older  than " $(( ${ndays} + 1 )) " days";
 echo "        (from under ${parentDir})";
 before=`find ${parentDir} | wc -l`;
 echo "            number of directories and files before cleaning: ${before}";