diff --git a/src/core/dbus-manager.c b/src/core/dbus-manager.c
index 73f739b12dcf6..20156c58f59fe 100644
--- a/src/core/dbus-manager.c
+++ b/src/core/dbus-manager.c
@@ -957,7 +957,7 @@ static int transient_unit_from_message(
 
         if (!unit_is_pristine(u))
                 return sd_bus_error_setf(error, BUS_ERROR_UNIT_EXISTS,
-                                         "Unit %s already exists.", name);
+                                         "Unit %s was already loaded or has a fragment file.", name);
 
         /* OK, the unit failed to load and is unreferenced, now let's
          * fill in the transient data instead */
diff --git a/src/core/unit.c b/src/core/unit.c
index 5016114cb470b..d0f71886132f5 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -4844,16 +4844,18 @@ int unit_fail_if_noncanonical(Unit *u, const char* where) {
 bool unit_is_pristine(Unit *u) {
         assert(u);
 
-        /* Check if the unit already exists or is already around,
-         * in a number of different ways. Note that to cater for unit
-         * types such as slice, we are generally fine with units that
-         * are marked UNIT_LOADED even though nothing was actually
-         * loaded, as those unit types don't require a file on disk. */
+        /* Check if the unit already exists or is already around, in a number of different ways. Note that to
+         * cater for unit types such as slice, we are generally fine with units that are marked UNIT_LOADED
+         * even though nothing was actually loaded, as those unit types don't require a file on disk.
+         *
+         * Note that we don't check for drop-ins here, because we allow drop-ins for transient units
+         * identically to non-transient units, both unit-specific and hierarchical. E.g. for a-b-c.service:
+         * service.d/….conf, a-.service.d/….conf, a-b-.service.d/….conf, a-b-c.service.d/….conf.
+         */
 
         return IN_SET(u->load_state, UNIT_NOT_FOUND, UNIT_LOADED) &&
                !u->fragment_path &&
                !u->source_path &&
-               strv_isempty(u->dropin_paths) &&
                !u->job &&
                !u->merged_into;
 }