diff --git a/include/tests_networking b/include/tests_networking
index fcf40802..c7c3a180 100644
--- a/include/tests_networking
+++ b/include/tests_networking
@@ -69,7 +69,8 @@
                 LogText "Result: hostnamed is defined and not longer than 63 characters"
             fi
             # Test valid characters (normally a dot should not be in the name, but we can't be 100% sure we have short name)
-            FIND=$(echo "${HOSTNAME}" | ${TRBINARY} -d '[:alnum:]\.\-')
+            # (we are NOT using [:alnum:] to support BusyBox's tr on devices with limited resources)
+            FIND=$(echo "${HOSTNAME}" | ${TRBINARY} -d '[a-zA-Z0-9]\.\-')
             if [ -z "${FIND}" ]; then
                 LogText "Result: good, no unexpected characters discovered in hostname"
                 if IsVerbose; then Display --indent 2 --text "- Hostname (allowed characters)" --result "${STATUS_OK}" --color GREEN; fi