diff --git a/coccinelle/empty-to-null.cocci b/coccinelle/empty-to-null.cocci
new file mode 100644
index 0000000000..fbc75b9c34
--- /dev/null
+++ b/coccinelle/empty-to-null.cocci
@@ -0,0 +1,5 @@
+@@
+expression s;
+@@
+- isempty(s) ? NULL : s
++ empty_to_null(s)
diff --git a/coccinelle/run-coccinelle.sh b/coccinelle/run-coccinelle.sh
index fe3aeb68ce..1373b53c5f 100755
--- a/coccinelle/run-coccinelle.sh
+++ b/coccinelle/run-coccinelle.sh
@@ -1,6 +1,6 @@
 #!/bin/bash -e
 
-for SCRIPT in *.cocci ; do
+for SCRIPT in ${@-*.cocci} ; do
         [ "$SCRIPT" = "empty-if.cocci" ] && continue
         echo "--x-- Processing $SCRIPT --x--"
         TMPFILE=`mktemp`
diff --git a/src/core/unit.c b/src/core/unit.c
index ed0cf02678..7af8425707 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -3015,8 +3015,8 @@ static int signal_name_owner_changed(sd_bus_message *message, void *userdata, sd
                 return 0;
         }
 
-        old_owner = isempty(old_owner) ? NULL : old_owner;
-        new_owner = isempty(new_owner) ? NULL : new_owner;
+        old_owner = empty_to_null(old_owner);
+        new_owner = empty_to_null(new_owner);
 
         if (UNIT_VTABLE(u)->bus_name_owner_change)
                 UNIT_VTABLE(u)->bus_name_owner_change(u, name, old_owner, new_owner);