diff --git a/tools_bin/ngcp-api-delete b/tools_bin/ngcp-api-delete
index 66aed2c269..94c0249e00 100755
--- a/tools_bin/ngcp-api-delete
+++ b/tools_bin/ngcp-api-delete
@@ -40,7 +40,7 @@ do
 			;;
 	esac
 done
-shift $(($OPTIND - 1))
+shift $((OPTIND - 1))
 
 URL="$1"
 if [ -z "$URL" ] ; then
diff --git a/tools_bin/ngcp-api-get b/tools_bin/ngcp-api-get
index d33bdab766..276330bb74 100755
--- a/tools_bin/ngcp-api-get
+++ b/tools_bin/ngcp-api-get
@@ -40,7 +40,7 @@ do
 			;;
 	esac
 done
-shift $(($OPTIND - 1))
+shift $((OPTIND - 1))
 
 URL="$1"
 if [ -z "$URL" ] ; then
diff --git a/tools_bin/ngcp-api-patch b/tools_bin/ngcp-api-patch
index 6d9fa4d34c..0e32fa2cda 100755
--- a/tools_bin/ngcp-api-patch
+++ b/tools_bin/ngcp-api-patch
@@ -55,7 +55,7 @@ do
 			;;
 	esac
 done
-shift $(($OPTIND - 1))
+shift $((OPTIND - 1))
 
 URL="$1"
 if [ -z "$URL" ] ; then
diff --git a/tools_bin/ngcp-api-post b/tools_bin/ngcp-api-post
index 39c6262a7a..58e0573034 100755
--- a/tools_bin/ngcp-api-post
+++ b/tools_bin/ngcp-api-post
@@ -49,7 +49,7 @@ do
 			;;
 	esac
 done
-shift $(($OPTIND - 1))
+shift $((OPTIND - 1))
 
 URL="$1"
 if [ -z "$URL" ] ; then
diff --git a/tools_bin/ngcp-api-put b/tools_bin/ngcp-api-put
index ecdd2a0117..bd0abca6e8 100755
--- a/tools_bin/ngcp-api-put
+++ b/tools_bin/ngcp-api-put
@@ -49,7 +49,7 @@ do
 			;;
 	esac
 done
-shift $(($OPTIND - 1))
+shift $((OPTIND - 1))
 
 URL="$1"
 if [ -z "$URL" ] ; then