diff --git a/nixos/tests/installed-tests/default.nix b/nixos/tests/installed-tests/default.nix
index b6bdfea22770..889a00d4b568 100644
--- a/nixos/tests/installed-tests/default.nix
+++ b/nixos/tests/installed-tests/default.nix
@@ -50,6 +50,12 @@ let
 
             environment.systemPackages = with pkgs; [ gnome-desktop-testing ];
 
+            # The installed tests need to be added to the test VM’s closure.
+            # Otherwise, their dependencies might not actually be registered
+            # as valid paths in the VM’s Nix store database,
+            # and `nix-store --query` commands run as part of the tests
+            # (for example when building Flatpak runtimes) will fail.
+            environment.variables.TESTED_PACKAGE_INSTALLED_TESTS = "${tested.installedTests}/share";
           };
 
           testScript =