diff --git a/git-tools/hooks/prepare-commit-msg b/git-tools/hooks/prepare-commit-msg
index f86bc6abc6..cedb342e58 100755
--- a/git-tools/hooks/prepare-commit-msg
+++ b/git-tools/hooks/prepare-commit-msg
@@ -31,17 +31,17 @@ branch="$(echo "$branch" | sed "s/refs\/heads\///g")"
 if [ "$2" = "" ]
 then
 	tail="";
-	ticket_id=$(sed -E 's/(ticket\/)(security\/)?([0-9]+)(.+$)?/\3/gm;t;d' <<< $branch);
-	branch_title=$(sed -E 's/(ticket\/)(security\/)?([0-9]+)(.+$)?/\1\2\3/gm;t;d' <<< $branch);
+	ticket_id=$(sed -E 's/(ticket\/)(security\/)?([0-9]+)(.+$)?/\3/gm;t;d' <<< "$branch");
+	branch_title=$(sed -E 's/(ticket\/)(security\/)?([0-9]+)(.+$)?/\1\2\3/gm;t;d' <<< "$branch");
 
-	if [ "security/" = "$(sed -E 's/(ticket\/)(security\/)?([0-9]+)(.+$)?/\2/gm;t;d' <<< $branch)" ];
+	if [ "security/" = "$(sed -E 's/(ticket\/)(security\/)?([0-9]+)(.+$)?/\2/gm;t;d' <<< "$branch")" ];
 	then
-		tail="$(printf "\n\nSECURITY-$ticket_id")";
+		tail="$(printf '\n\nSECURITY-%s' "$ticket_id")";
 	else
 		# Branch is prefixed with 'ticket/', append ticket ID to message
 		if [ "$branch" != "${branch##ticket/}" ];
 		then
-			tail="$(printf "\n\nPHPBB3-$ticket_id")";
+			tail="$(printf '\n\nPHPBB3-%s' "$ticket_id")";
 		fi
 	fi