diff --git a/internal/api/client_assets.go b/internal/api/client_assets.go
index b39dbff0..10bfff77 100644
--- a/internal/api/client_assets.go
+++ b/internal/api/client_assets.go
@@ -89,7 +89,7 @@ func (h *handlers) handleClientAPK(w http.ResponseWriter, r *http.Request) {
 		writeErrWithLog(w, h.logger, "client_apk: open", err)
 		return
 	}
-	defer f.Close()
+	defer func() { _ = f.Close() }()
 
 	stat, err := f.Stat()
 	if err != nil {
diff --git a/internal/api/client_assets_test.go b/internal/api/client_assets_test.go
index e5bdc952..3323cc16 100644
--- a/internal/api/client_assets_test.go
+++ b/internal/api/client_assets_test.go
@@ -17,13 +17,13 @@ func withClientAPKDir(t *testing.T) string {
 	t.Helper()
 	dir := t.TempDir()
 	prev, hadPrev := os.LookupEnv("MINSTREL_CLIENT_APK_DIR")
-	os.Setenv("MINSTREL_CLIENT_APK_DIR", dir)
+	t.Setenv("MINSTREL_CLIENT_APK_DIR", dir)
 	t.Cleanup(func() {
 		if hadPrev {
-			os.Setenv("MINSTREL_CLIENT_APK_DIR", prev)
-		} else {
-			os.Unsetenv("MINSTREL_CLIENT_APK_DIR")
+			t.Setenv("MINSTREL_CLIENT_APK_DIR", prev)
 		}
+		// t.Setenv auto-restores the prior empty/unset state at end of
+		// test, so the !hadPrev branch needs no explicit Unsetenv.
 	})
 	return dir
 }