diff --git a/dlls/wininet/tests/internet.c b/dlls/wininet/tests/internet.c
index 0f1e8450292..2f88f586ceb 100644
--- a/dlls/wininet/tests/internet.c
+++ b/dlls/wininet/tests/internet.c
@@ -73,6 +73,16 @@ static void test_InternetCanonicalizeUrlA(void)
         "got %u and %u with size %u for '%s' (%d)\n",
         res, GetLastError(), dwSize, buffer, lstrlenA(buffer));
 
+    memset(buffer, '#', sizeof(buffer)-1);
+    buffer[sizeof(buffer)-1] = '\0';
+    dwSize = sizeof(buffer);
+    SetLastError(0xdeadbeef);
+    res = InternetCanonicalizeUrlA("file:///C:/Program%20Files/Atmel/AVR%20Tools/STK500/STK500.xml", buffer, &dwSize, ICU_DECODE | ICU_NO_ENCODE);
+    ok(res, "InternetCanonicalizeUrlA failed %u\n", GetLastError());
+    ok(dwSize == lstrlenA(buffer), "got %d expected %d\n", dwSize, lstrlenA(buffer));
+    todo_wine ok(!lstrcmpA("file://C:\\Program Files\\Atmel\\AVR Tools\\STK500\\STK500.xml", buffer),
+       "got %s expected 'file://C:\\Program Files\\Atmel\\AVR Tools\\STK500\\STK500.xml'\n", buffer);
+
     /* buffer is larger as the required size */
     memset(buffer, '#', sizeof(buffer)-1);
     buffer[sizeof(buffer)-1] = '\0';