diff --git a/userapi/internal/device_list_update_test.go b/userapi/internal/device_list_update_test.go
index 1b9e4b5c3..38fd8b583 100644
--- a/userapi/internal/device_list_update_test.go
+++ b/userapi/internal/device_list_update_test.go
@@ -433,6 +433,7 @@ func Test_dedupeStateList(t *testing.T) {
 	alice := "@alice:localhost"
 	bob := "@bob:localhost"
 	charlie := "@charlie:notlocalhost"
+	invalidUserID := "iaminvalid:localhost"
 
 	tests := []struct {
 		name       string
@@ -459,6 +460,11 @@ func Test_dedupeStateList(t *testing.T) {
 			staleLists: []string{alice, bob, charlie},
 			want:       []string{alice, charlie},
 		},
+		{
+			name:       "list with invalid userID",
+			staleLists: []string{alice, bob, invalidUserID},
+			want:       []string{alice},
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {