diff --git a/src/modules/systemd/libzbxsystemd.c b/src/modules/systemd/libzbxsystemd.c
index c24a034..dc72fed 100644
--- a/src/modules/systemd/libzbxsystemd.c
+++ b/src/modules/systemd/libzbxsystemd.c
@@ -211,8 +211,8 @@ static int SYSTEMD_UNIT_DISCOVERY(AGENT_REQUEST *request, AGENT_RESULT *result)
       switch (i) {
       case 0:
         // filter by unit type
-        if(NULL != filter || '\0' != filter)
-          if(0 == systemd_cmptype(value.str, filter))
+        if(NULL != filter && '\0' != *filter)
+           if (0 == systemd_cmptype(value.str, filter))
             goto next_unit;
 
         zbx_json_addobject(&j, NULL);