diff --git a/dlls/dwrite/tests/layout.c b/dlls/dwrite/tests/layout.c
index 38b818c0169..8a323032370 100644
--- a/dlls/dwrite/tests/layout.c
+++ b/dlls/dwrite/tests/layout.c
@@ -602,6 +602,7 @@ static HRESULT WINAPI testrenderer_DrawGlyphRun(IDWriteTextRenderer *iface,
     entry.kind = DRAW_GLYPHRUN;
     if (effect)
         entry.kind |= DRAW_EFFECT;
+    ok(lstrlenW(descr->localeName) < LOCALE_NAME_MAX_LENGTH, "unexpectedly long locale name\n");
     lstrcpyW(entry.locale, descr->localeName);
     entry.glyphcount = run->glyphCount;
     add_call(sequences, RENDERER_ID, &entry);