diff --git a/dlls/advapi32/registry.c b/dlls/advapi32/registry.c
index 0697c9c5e27..30130b1bfa9 100644
--- a/dlls/advapi32/registry.c
+++ b/dlls/advapi32/registry.c
@@ -1049,18 +1049,18 @@ LSTATUS WINAPI RegQueryInfoKeyA( HKEY hkey, LPSTR class, LPDWORD class_len, LPDW
 
         if (status) goto done;
 
-        RtlUnicodeToMultiByteSize( &len, (WCHAR *)(buf_ptr + info->ClassOffset), info->ClassLength);
-        if (class_len)
+        len = 0;
+        if (class && class_len) len = *class_len;
+        RtlUnicodeToMultiByteN( class, len, class_len,
+                                (WCHAR *)(buf_ptr + info->ClassOffset), info->ClassLength );
+        if (len)
         {
-            if (*class_len == 0) class = NULL;
-            if (class && len + 1 > *class_len) status = STATUS_BUFFER_OVERFLOW;
-            *class_len = len;
-        }
-        if (class && !status)
-        {
-            RtlUnicodeToMultiByteN( class, len, NULL, (WCHAR *)(buf_ptr + info->ClassOffset),
-                                    info->ClassLength );
-            class[len] = 0;
+            class[len - 1] = 0;
+            if (*class_len + 1 > len)
+            {
+                status = STATUS_BUFFER_OVERFLOW;
+                *class_len -= 1;
+            }
         }
     }
     else status = STATUS_SUCCESS;
diff --git a/dlls/advapi32/tests/registry.c b/dlls/advapi32/tests/registry.c
index 2aca8373608..c8013845607 100644
--- a/dlls/advapi32/tests/registry.c
+++ b/dlls/advapi32/tests/registry.c
@@ -1815,10 +1815,10 @@ static void test_reg_query_info(void)
     classlen = 1;
     ret = RegQueryInfoKeyA(subkey, classbuffer, &classlen, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
     ok(ret == ERROR_MORE_DATA, "ret = %d\n", ret);
-    todo_wine ok(classlen == 0, "classlen = %u\n", classlen);
+    ok(classlen == 0, "classlen = %u\n", classlen);
     memset(expectbuffer, 0x55, sizeof(expectbuffer));
     expectbuffer[0] = 0;
-    todo_wine ok(!memcmp(classbuffer, expectbuffer, sizeof(classbuffer)), "classbuffer was modified\n");
+    ok(!memcmp(classbuffer, expectbuffer, sizeof(classbuffer)), "classbuffer was modified\n");
 
     memset(classbufferW, 0x55, sizeof(classbufferW));
     classlen = 1;
@@ -1834,12 +1834,12 @@ static void test_reg_query_info(void)
     classlen = sizeof(subkey_class) - 1;
     ret = RegQueryInfoKeyA(subkey, classbuffer, &classlen, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
     ok(ret == ERROR_MORE_DATA, "ret = %d\n", ret);
-    todo_wine ok(classlen == sizeof(subkey_class) - 2, "classlen = %u\n", classlen);
+    ok(classlen == sizeof(subkey_class) - 2, "classlen = %u\n", classlen);
     memset(expectbuffer, 0x55, sizeof(expectbuffer));
     strcpy(expectbuffer, subkey_class);
     expectbuffer[sizeof(subkey_class) - 2] = 0;
     expectbuffer[sizeof(subkey_class) - 1] = 0x55;
-    todo_wine ok(!memcmp(classbuffer, expectbuffer, sizeof(classbuffer)),
+    ok(!memcmp(classbuffer, expectbuffer, sizeof(classbuffer)),
        "classbuffer = %.*s, expected %s\n",
        (int)sizeof(classbuffer), classbuffer, expectbuffer);