diff --git a/TODO b/TODO
index ac4be8bf..7a44a200 100644
--- a/TODO
+++ b/TODO
@@ -26,8 +26,6 @@
   - show maildirs as a tree, not a list in speed bar
   - mark message, decide what to do with them later
   - make killing all windows (i.e.. 'fullscreen mode' optional)
-  - *BUG* don't remove unknown message flags when moving (see
-    https://github.com/djcb/mu/issues/20)
   - improve fringe marks (see https://github.com/djcb/mu/issues/21)
 
 ** Done
@@ -52,6 +50,8 @@
   - *FIX* fix for strings where len (g_utf8_strdown (str)) > len (str)
   - make sure marks correspond to the *current* message in message view (see
     https://github.com/djcb/mu/issues/26)
+  - *FIX* don't remove unknown message flags when moving (see
+    https://github.com/djcb/mu/issues/20)
 
 
 
diff --git a/lib/mu-maildir.c b/lib/mu-maildir.c
index cf8b77bb..82721d19 100644
--- a/lib/mu-maildir.c
+++ b/lib/mu-maildir.c
@@ -711,7 +711,8 @@ mu_maildir_get_flags_from_path (const char *path)
  *
  */
 static gchar*
-get_new_path (const char *mdir, const char *mfile, MuFlags flags)
+get_new_path (const char *mdir, const char *mfile, MuFlags flags,
+	      const char* custom_flags)
 {
 	if (flags & MU_FLAG_NEW)
 		return g_strdup_printf ("%s%cnew%c%s",
@@ -721,9 +722,10 @@ get_new_path (const char *mdir, const char *mfile, MuFlags flags)
 		const char *flagstr;
 		flagstr = mu_flags_to_str_s (flags, MU_FLAG_TYPE_MAILFILE);
 
-		return g_strdup_printf ("%s%ccur%c%s:2,%s",
+		return g_strdup_printf ("%s%ccur%c%s:2,%s%s",
 					mdir, G_DIR_SEPARATOR, G_DIR_SEPARATOR,
-					mfile, flagstr);
+					mfile, flagstr,
+					custom_flags ? custom_flags : "");
 	}
 }
 
@@ -755,32 +757,35 @@ char*
 mu_maildir_get_new_path (const char *oldpath, const char *new_mdir,
 			 MuFlags newflags)
 {
-	char *mfile, *mdir, *newpath, *cur;
+	char *mfile, *mdir, *custom_flags, *newpath, *cur;
 
 	g_return_val_if_fail (oldpath, NULL);
 
-	mfile = newpath = NULL;
+	mfile = newpath = custom_flags = NULL;
 
 	/* determine the maildir */
 	mdir = mu_maildir_get_maildir_from_path (oldpath);
 	if (!mdir)
 		return NULL;
 
-	/* determine the name of the mailfile, stripped of its flags */
+	/* determine the name of the mailfile, stripped of its flags, as well
+	 * as any custom (non-standard) flags */
 	mfile = g_path_get_basename (oldpath);
 	for (cur = &mfile[strlen(mfile)-1]; cur > mfile; --cur) {
 		if ((*cur == ':' || *cur == '!') &&
 		    (cur[1] == '2' && cur[2] == ',')) {
+			/* get the custom flags (if any) */
+			custom_flags = mu_flags_custom_from_str (cur + 3);
 			cur[0] = '\0'; /* strip the flags */
 			break;
 		}
 	}
 
 	newpath = get_new_path (new_mdir ? new_mdir : mdir,
-				mfile, newflags);
-
+				mfile, newflags, custom_flags);
 	g_free (mfile);
 	g_free (mdir);
+	g_free (custom_flags);
 
 	return newpath;
 }
diff --git a/lib/tests/test-mu-maildir.c b/lib/tests/test-mu-maildir.c
index c2853185..59c72f0d 100644
--- a/lib/tests/test-mu-maildir.c
+++ b/lib/tests/test-mu-maildir.c
@@ -517,6 +517,43 @@ test_mu_maildir_get_new_path_02 (void)
 }
 
 
+static void
+test_mu_maildir_get_new_path_custom (void)
+{
+	int i;
+
+	struct {
+		const char *oldpath;
+		MuFlags flags;
+		const char *targetdir;
+		const char *newpath;
+	} paths[] = {
+		{
+			"/home/foo/Maildir/test/cur/123456:2,FR",
+			MU_FLAG_REPLIED, "/home/foo/Maildir/blabla",
+			"/home/foo/Maildir/blabla/cur/123456:2,R"
+		}, {
+			"/home/foo/Maildir/test/cur/123456:2,hFeRllo123",
+			MU_FLAG_FLAGGED, "/home/foo/Maildir/blabla",
+			"/home/foo/Maildir/blabla/cur/123456:2,Fhello123"
+		}, {
+			"/home/foo/Maildir/test/cur/123456:2,abc",
+			MU_FLAG_PASSED, "/home/foo/Maildir/blabla",
+			"/home/foo/Maildir/blabla/cur/123456:2,Pabc"
+		}
+	};
+
+	for (i = 0; i != G_N_ELEMENTS(paths); ++i) {
+		gchar *str;
+		str = mu_maildir_get_new_path(paths[i].oldpath,
+					      paths[i].targetdir,
+					      paths[i].flags);
+		g_assert_cmpstr(str, ==, paths[i].newpath);
+		g_free(str);
+	}
+}
+
+
 
 static void
 test_mu_maildir_get_maildir_from_path (void)
@@ -573,6 +610,8 @@ main (int argc, char *argv[])
 			test_mu_maildir_get_new_path_01);
 	g_test_add_func("/mu-maildir/mu-maildir-get-new-path-02",
 			test_mu_maildir_get_new_path_02);
+	g_test_add_func("/mu-maildir/mu-maildir-get-new-path-custom",
+			test_mu_maildir_get_new_path_custom);
 	g_test_add_func("/mu-maildir/mu-maildir-get-flags-from-path",
 			test_mu_maildir_get_flags_from_path);