diff --git a/target/scripts/startup/setup.d/postfix.sh b/target/scripts/startup/setup.d/postfix.sh
index eb830760..34b35e6e 100644
--- a/target/scripts/startup/setup.d/postfix.sh
+++ b/target/scripts/startup/setup.d/postfix.sh
@@ -170,8 +170,8 @@ function _setup_SRS
 
   if [[ -n ${SRS_EXCLUDE_DOMAINS} ]]
   then
-    sed -i \
-      "s/^#\?(SRS_EXCLUDE_DOMAINS=).*$/\1=${SRS_EXCLUDE_DOMAINS}/g" \
+    sedfile -i -E \
+      "s|^#?(SRS_EXCLUDE_DOMAINS=).*|\1${SRS_EXCLUDE_DOMAINS}|" \
       /etc/default/postsrsd
   fi
 }