diff --git a/frontend/src/ts/test/test-ui.ts b/frontend/src/ts/test/test-ui.ts
index 0b3f727c8174..e70bce04f8b9 100644
--- a/frontend/src/ts/test/test-ui.ts
+++ b/frontend/src/ts/test/test-ui.ts
@@ -856,7 +856,7 @@ export async function updateWordLetters({
               `<letter class="incorrect ${tabChar}${nlChar}">` +
               (Config.indicateTypos === "replace" ||
               Config.indicateTypos === "both"
-                ? inputChars[i] === " "
+                ? inputChars[i] === " " || inputChars[i] === "\t"
                   ? "_"
                   : inputChars[i]
                 : currentLetter) +