diff --git a/src/core/execute.c b/src/core/execute.c
index a7082310ba..0695527968 100644
--- a/src/core/execute.c
+++ b/src/core/execute.c
@@ -1839,7 +1839,7 @@ static bool exec_needs_mount_namespace(
         if (context->n_temporary_filesystems > 0)
                 return true;
 
-        if (context->mount_flags != 0)
+        if (!IN_SET(context->mount_flags, 0, MS_SHARED))
                 return true;
 
         if (context->private_tmp && runtime && (runtime->tmp_dir || runtime->var_tmp_dir))
@@ -2435,6 +2435,9 @@ static int apply_mount_namespace(
         else
                 ns_info = (NamespaceInfo) {};
 
+        if (context->mount_flags == MS_SHARED)
+                log_unit_debug(u, "shared mount propagation hidden by other fs namespacing unit settings: ignoring");
+
         r = setup_namespace(root_dir, root_image,
                             &ns_info, context->read_write_paths,
                             needs_sandboxing ? context->read_only_paths : NULL,