diff --git a/dlls/dwrite/main.c b/dlls/dwrite/main.c
index b056cb101e1..4ddc74bf45a 100644
--- a/dlls/dwrite/main.c
+++ b/dlls/dwrite/main.c
@@ -271,8 +271,16 @@ static HRESULT WINAPI localizedstrings_GetLocaleName(IDWriteLocalizedStrings *if
 static HRESULT WINAPI localizedstrings_GetStringLength(IDWriteLocalizedStrings *iface, UINT32 index, UINT32 *length)
 {
     struct localizedstrings *This = impl_from_IDWriteLocalizedStrings(iface);
-    FIXME("(%p)->(%u %p): stub\n", This, index, length);
-    return E_NOTIMPL;
+
+    TRACE("(%p)->(%u %p)\n", This, index, length);
+
+    if (index >= This->count) {
+        *length = (UINT32)-1;
+        return E_FAIL;
+    }
+
+    *length = strlenW(This->data[index].string);
+    return S_OK;
 }
 
 static HRESULT WINAPI localizedstrings_GetString(IDWriteLocalizedStrings *iface, UINT32 index, WCHAR *buffer, UINT32 size)
diff --git a/dlls/dwrite/tests/font.c b/dlls/dwrite/tests/font.c
index 3bba1ca88fb..b22453cb475 100644
--- a/dlls/dwrite/tests/font.c
+++ b/dlls/dwrite/tests/font.c
@@ -321,6 +321,7 @@ static void test_GetFamilyNames(void)
     IDWriteFont *font;
     LOGFONTW logfont;
     HRESULT hr;
+    UINT32 len;
 
     hr = IDWriteFactory_GetGdiInterop(factory, &interop);
     EXPECT_HR(hr, S_OK);
@@ -350,9 +351,24 @@ if (0) /* crashes on native */
     EXPECT_REF(names2, 1);
     ok(names != names2, "got %p, was %p\n", names2, names);
 
-    IDWriteLocalizedStrings_Release(names);
     IDWriteLocalizedStrings_Release(names2);
 
+    /* GetStringLength */
+if (0) /* crashes on native */
+    hr = IDWriteLocalizedStrings_GetStringLength(names, 0, NULL);
+
+    len = 0;
+    hr = IDWriteLocalizedStrings_GetStringLength(names, 0, &len);
+    ok(hr == S_OK, "got 0x%08x\n", hr);
+    ok(len > 0, "got %u\n", len);
+
+    len = 100;
+    hr = IDWriteLocalizedStrings_GetStringLength(names, 10, &len);
+    ok(hr == E_FAIL, "got 0x%08x\n", hr);
+    ok(len == (UINT32)-1, "got %u\n", len);
+
+    IDWriteLocalizedStrings_Release(names);
+
     IDWriteFontFamily_Release(family);
     IDWriteFont_Release(font);
     IDWriteGdiInterop_Release(interop);