diff --git a/bin/infra b/bin/infra
index 9bdcdae..ba16d8c 100755
--- a/bin/infra
+++ b/bin/infra
@@ -204,7 +204,7 @@ function destroy() {
 function provision() {
     # If INFRA_PREFIX has not been set yet, request it from user
     if [ -z "$INFRA_PREFIX" ]; then
-        DEFAULT_INFRA_PREFIX=$(tr -dc 'a-zA-Z0-9' < /dev/urandom | fold -w 8 | head -n 1)
+        DEFAULT_INFRA_PREFIX=$(tr -dc 'a-z0-9' < /dev/urandom | fold -w 8 | head -n 1)
 
         warnb << EOF
 # Infrastructure Prefix