diff --git a/salt/common/tools/sbin/so-common b/salt/common/tools/sbin/so-common
index 4909bc5e1..9382fe472 100755
--- a/salt/common/tools/sbin/so-common
+++ b/salt/common/tools/sbin/so-common
@@ -158,14 +158,14 @@ wait_for_apt() {
 	local count=0
 	while [[ "$count" -lt "$retry_count" ]]; do
 		if __check_apt_lock; then
-			if [ -z "$progress_callback" ]; then
+			if [[ -z $progress_callback ]]; then
 				echo "$lock_msg"
 				echo "$retry_msg" 
 			else
 				$progress_callback "$retry_msg"
 			fi
 		else
-			$progress_callback "$old_text"
+			[[ -z $progress_callback ]] && $progress_callback "$old_text"
 			return 0
 		fi
 		sleep "$retry_timeout"