diff --git a/lib/upgrade/upgrade_supported.go b/lib/upgrade/upgrade_supported.go
index 80312a6fa..74b1ae899 100644
--- a/lib/upgrade/upgrade_supported.go
+++ b/lib/upgrade/upgrade_supported.go
@@ -391,7 +391,7 @@ func verifyUpgrade(archiveName, tempName string, sig []byte) error {
 	// multireader. This ensures that it is not only a bonafide syncthing
 	// binary, but it is also of exactly the platform and version we expect.
 
-	mr := io.MultiReader(bytes.NewBufferString(archiveName+"\n"), fd)
+	mr := io.MultiReader(strings.NewReader(archiveName+"\n"), fd)
 	err = signature.Verify(SigningKey, sig, mr)
 	fd.Close()