diff --git a/routers/api/packages/alpine/alpine.go b/routers/api/packages/alpine/alpine.go
index d3560dc4b99..9a593f7caa2 100644
--- a/routers/api/packages/alpine/alpine.go
+++ b/routers/api/packages/alpine/alpine.go
@@ -67,15 +67,34 @@ func GetRepositoryFile(ctx *context.Context) {
 		return
 	}
 
+	branch := ctx.PathParam("branch")
+	repository := ctx.PathParam("repository")
+	architecture := ctx.PathParam("architecture")
+
 	s, u, pf, err := packages_service.OpenFileForDownloadByPackageVersion(
 		ctx,
 		pv,
 		&packages_service.PackageFileInfo{
 			Filename:     alpine_service.IndexArchiveFilename,
-			CompositeKey: fmt.Sprintf("%s|%s|%s", ctx.PathParam("branch"), ctx.PathParam("repository"), ctx.PathParam("architecture")),
+			CompositeKey: fmt.Sprintf("%s|%s|%s", branch, repository, architecture),
 		},
 		ctx.Req.Method,
 	)
+	// A repository that only contains "noarch" packages has no per-architecture
+	// index. Since noarch packages are installable on every architecture, fall
+	// back to the noarch index so clients requesting their own architecture
+	// (e.g. x86_64) can still discover them.
+	if errors.Is(err, util.ErrNotExist) && architecture != alpine_module.NoArch {
+		s, u, pf, err = packages_service.OpenFileForDownloadByPackageVersion(
+			ctx,
+			pv,
+			&packages_service.PackageFileInfo{
+				Filename:     alpine_service.IndexArchiveFilename,
+				CompositeKey: fmt.Sprintf("%s|%s|%s", branch, repository, alpine_module.NoArch),
+			},
+			ctx.Req.Method,
+		)
+	}
 	if err != nil {
 		if errors.Is(err, util.ErrNotExist) {
 			apiError(ctx, http.StatusNotFound, err)
diff --git a/tests/integration/api_packages_alpine_test.go b/tests/integration/api_packages_alpine_test.go
index 0fe158e7f04..5b097534e28 100644
--- a/tests/integration/api_packages_alpine_test.go
+++ b/tests/integration/api_packages_alpine_test.go
@@ -268,6 +268,36 @@ AACAX/AKARNTyAAoAAA=`
 						AddBasicAuth(user.Name)
 					MakeRequest(t, req, http.StatusNoContent)
 				})
+
+				t.Run("NoArchOnly", func(t *testing.T) {
+					defer tests.PrintCurrentTest(t)()
+
+					// A repository that only contains noarch packages has no per-architecture index,
+					// but apk always requests the index for its own architecture (e.g. x86_64).
+					// That request must fall back to the noarch index instead of 404ing.
+					noarchRepository := repository + "-noarchonly"
+
+					req := NewRequestWithBody(t, "PUT", fmt.Sprintf("%s/%s/%s", rootURL, branch, noarchRepository), bytes.NewReader(noarchContent)).
+						AddBasicAuth(user.Name)
+					MakeRequest(t, req, http.StatusCreated)
+
+					req = NewRequest(t, "GET", fmt.Sprintf("%s/%s/%s/x86_64/APKINDEX.tar.gz", rootURL, branch, noarchRepository))
+					resp := MakeRequest(t, req, http.StatusOK)
+
+					content, err := readIndexContent(resp.Body)
+					assert.NoError(t, err)
+
+					assert.Contains(t, content, "C:Q1kbH5WoIPFccQYyATanaKXd2cJcc=\n")
+					assert.Contains(t, content, "A:noarch\n")
+
+					// The noarch index is still directly retrievable too.
+					req = NewRequest(t, "GET", fmt.Sprintf("%s/%s/%s/noarch/APKINDEX.tar.gz", rootURL, branch, noarchRepository))
+					MakeRequest(t, req, http.StatusOK)
+
+					req = NewRequest(t, "DELETE", fmt.Sprintf("%s/%s/%s/noarch/gitea-noarch-1.4-r0.apk", rootURL, branch, noarchRepository)).
+						AddBasicAuth(user.Name)
+					MakeRequest(t, req, http.StatusNoContent)
+				})
 			})
 		}
 	}