diff --git a/testsuite/tests/ada_api/gpr2_project_unit_provider/test.yaml b/testsuite/tests/ada_api/gpr2_project_unit_provider/test.yaml
index 357b9b072..977f8d432 100644
--- a/testsuite/tests/ada_api/gpr2_project_unit_provider/test.yaml
+++ b/testsuite/tests/ada_api/gpr2_project_unit_provider/test.yaml
@@ -1,2 +1,8 @@
 driver: ada-api
 main: main.adb
+control:
+    - [
+        XFAIL,
+        valgrind,
+        "eng/gpr/gpr-issues#406: GPR2 slowness, test times out"
+    ]