diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1cb9bbf..3044f8e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## (unreleased)
 
+### Internal
+
+- make shell variables lower-case to avoid conflicts with system variables
+
 ## 1.0.0 (2017-11-17)
 
 Initial release
diff --git a/random-password b/random-password
index c127f62..e01ef9b 100755
--- a/random-password
+++ b/random-password
@@ -1,3 +1,3 @@
 #!/bin/bash
-LENGTH=${1:-32}
-cat /dev/urandom | tr -dc 'a-zA-Z0-9-_!@#$%^&*()_+{}|:<>?=' | fold -w $LENGTH | head -n 1 | grep -i '[!@#$%^&*()_+{}|:<>?=]'
+length=${1:-32}
+cat /dev/urandom | tr -dc 'a-zA-Z0-9-_!@#$%^&*()_+{}|:<>?=' | fold -w $length | head -n 1 | grep -i '[!@#$%^&*()_+{}|:<>?=]'