diff -up ./src/polkit/polkitunixprocess.c.ori ./src/polkit/polkitunixprocess.c
--- ./src/polkit/polkitunixprocess.c.ori	2019-02-06 16:47:23.460666237 +0100
+++ ./src/polkit/polkitunixprocess.c	2019-02-06 16:47:43.846573792 +0100
@@ -211,14 +211,9 @@ polkit_unix_process_set_property (GObjec
       polkit_unix_process_set_pid (unix_process, g_value_get_int (value));
       break;
 
-    case PROP_UID: {
-      gint val;
-
-      val = g_value_get_int (value);
-      g_return_if_fail (val != -1);
-      polkit_unix_process_set_uid (unix_process, val);
+    case PROP_UID:
+      polkit_unix_process_set_uid (unix_process, g_value_get_int (value));
       break;
-    }
 
     case PROP_START_TIME:
       polkit_unix_process_set_start_time (unix_process, g_value_get_uint64 (value));