diff --git a/ssm b/ssm
index 2b6e455..bc06982 100755
--- a/ssm
+++ b/ssm
@@ -3,6 +3,7 @@ shopt -s nullglob
 
 # Utility functions
 is_function() [[ $(type -t $1 2>/dev/null) == 'function' ]]
+readonly -f is_function
 
 var() {
 	declare varname=$1; shift
@@ -97,7 +98,7 @@ var() {
 			;;
 		esac
 	fi
-}
+}; readonly -f var
 
 ## Die. Why not?
 die() {