diff --git a/modules/git/functions/is-true b/modules/git/functions/is-true
index 5b0baed..41d9fca 100644
--- a/modules/git/functions/is-true
+++ b/modules/git/functions/is-true
@@ -1,3 +1,3 @@
 # Checks a boolean variable for "true".
 # Case insensitive: "1", "y", "yes", "t", "true", "o", and "on".
-[[ -n "$1" && "$1" == (1|[Yy]([Ee][Ss]|)|[Tt]([Rr][Uu][Ee]|)|[Oo]([Nn]|)) ]]
+[[ -n ${1} && ${1} == (1|[Yy]([Ee][Ss]|)|[Tt]([Rr][Uu][Ee]|)|[Oo]([Nn]|)) ]]