diff --git a/dlls/user/tests/.cvsignore b/dlls/user/tests/.cvsignore
index cbda497..8fc4c87 100644
--- a/dlls/user/tests/.cvsignore
+++ b/dlls/user/tests/.cvsignore
@@ -1,5 +1,6 @@
 Makefile
 class.ok
+clipboard.ok
 dde.ok
 dialog.ok
 generated.ok
diff --git a/dlls/user/tests/Makefile.in b/dlls/user/tests/Makefile.in
index f3c5e07..eceb1cc 100644
--- a/dlls/user/tests/Makefile.in
+++ b/dlls/user/tests/Makefile.in
@@ -7,6 +7,7 @@
 
 CTESTS = \
 	class.c \
+	clipboard.c \
 	dde.c \
 	dialog.c \
 	generated.c \
diff --git a/dlls/user/tests/clipboard.c b/dlls/user/tests/clipboard.c
new file mode 100644
index 0000000..59108d6
--- /dev/null
+++ b/dlls/user/tests/clipboard.c
@@ -0,0 +1,188 @@
+/*
+ * Unit test suite for clipboard functions.
+ *
+ * Copyright 2002 Dmitry Timoshkov
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include "wine/test.h"
+#include "winbase.h"
+#include "winerror.h"
+#include "winuser.h"
+
+static BOOL is_win9x = FALSE;
+
+#define test_last_error(expected_error) \
+    do \
+    { \
+        if (!is_win9x) \
+            ok(GetLastError() == expected_error, \
+               "Last error should be set to %d, not %ld\n", \
+                expected_error, GetLastError()); \
+    } while (0)
+
+static void test_ClipboardOwner(void)
+{
+    HWND hWnd1, hWnd2;
+
+    SetLastError(0xdeadbeef);
+    ok(!GetClipboardOwner() && GetLastError() == 0xdeadbeef,
+       "could not perform clipboard test: clipboard already owned\n");
+
+    hWnd1 = CreateWindowExA(0, "static", NULL, WS_POPUP,
+                                 0, 0, 10, 10, 0, 0, 0, NULL);
+    ok(hWnd1 != 0, "CreateWindowExA error %ld\n", GetLastError());
+    trace("hWnd1 = %p\n", hWnd1);
+
+    hWnd2 = CreateWindowExA(0, "static", NULL, WS_POPUP,
+                                 0, 0, 10, 10, 0, 0, 0, NULL);
+    ok(hWnd2 != 0, "CreateWindowExA error %ld\n", GetLastError());
+    trace("hWnd2 = %p\n", hWnd2);
+
+    SetLastError(0xdeadbeef);
+    ok(!CloseClipboard(), "CloseClipboard should fail if clipboard wasn't open\n");
+    test_last_error(ERROR_CLIPBOARD_NOT_OPEN);
+
+    ok(OpenClipboard(0), "OpenClipboard failed\n");
+    ok(!GetClipboardOwner(), "clipboard should still be not owned\n");
+    ok(!OpenClipboard(hWnd1), "OpenClipboard should fail since clipboard already opened\n");
+    ok(CloseClipboard(), "CloseClipboard error %ld\n", GetLastError());
+
+    ok(OpenClipboard(hWnd1), "OpenClipboard failed\n");
+
+    SetLastError(0xdeadbeef);
+    ok(!OpenClipboard(hWnd2) && GetLastError() == 0xdeadbeef,
+       "OpenClipboard should fail without setting last error value\n");
+
+    SetLastError(0xdeadbeef);
+    ok(!GetClipboardOwner() && GetLastError() == 0xdeadbeef, "clipboard should still be not owned\n");
+    ok(EmptyClipboard(), "EmptyClipboard error %ld\n", GetLastError());
+    ok(GetClipboardOwner() == hWnd1, "clipboard should be owned by %p, not by %p\n", hWnd1, GetClipboardOwner());
+
+    SetLastError(0xdeadbeef);
+    ok(!OpenClipboard(hWnd2) && GetLastError() == 0xdeadbeef,
+       "OpenClipboard should fail without setting last error value\n");
+
+    ok(CloseClipboard(), "CloseClipboard error %ld", GetLastError());
+    ok(GetClipboardOwner() == hWnd1, "clipboard should still be owned\n");
+
+    ok(DestroyWindow(hWnd1), "DestroyWindow error %ld\n", GetLastError());
+    ok(DestroyWindow(hWnd2), "DestroyWindow error %ld\n", GetLastError());
+    SetLastError(0xdeadbeef);
+    ok(!GetClipboardOwner() && GetLastError() == 0xdeadbeef, "clipboard should not be owned\n");
+}
+
+static void test_RegisterClipboardFormatA(void)
+{
+    ATOM atom_id;
+    UINT format_id, format_id2;
+    char buf[256];
+    int len;
+
+    format_id = RegisterClipboardFormatA("my_cool_clipboard_format");
+    ok(format_id > 0xc000 && format_id < 0xffff, "invalid clipboard format id %04x\n", format_id);
+
+    format_id2 = RegisterClipboardFormatA("MY_COOL_CLIPBOARD_FORMAT");
+    ok(format_id2 == format_id, "invalid clipboard format id %04x\n", format_id2);
+
+    len = GetClipboardFormatNameA(format_id, buf, 256);
+    ok(len == lstrlenA("my_cool_clipboard_format"), "wrong format name length %d\n", len);
+    ok(!lstrcmpA(buf, "my_cool_clipboard_format"), "wrong format name \"%s\"\n", buf);
+
+    lstrcpyA(buf, "foo");
+    SetLastError(0xdeadbeef);
+    len = GetAtomNameA((ATOM)format_id, buf, 256);
+    ok(len == 0, "GetAtomNameA should fail\n");
+    test_last_error(ERROR_INVALID_HANDLE);
+
+todo_wine
+{
+    lstrcpyA(buf, "foo");
+    SetLastError(0xdeadbeef);
+    len = GlobalGetAtomNameA((ATOM)format_id, buf, 256);
+    ok(len == 0, "GlobalGetAtomNameA should fail\n");
+    test_last_error(ERROR_INVALID_HANDLE);
+}
+
+    SetLastError(0xdeadbeef);
+    atom_id = FindAtomA("my_cool_clipboard_format");
+    ok(atom_id == 0, "FindAtomA should fail\n");
+    test_last_error(ERROR_FILE_NOT_FOUND);
+
+#if 0
+    /* this relies on the clipboard and global atom table being different */
+    SetLastError(0xdeadbeef);
+    atom_id = GlobalFindAtomA("my_cool_clipboard_format");
+    ok(atom_id == 0, "GlobalFindAtomA should fail\n");
+    test_last_error(ERROR_FILE_NOT_FOUND);
+
+    for (format_id = 0; format_id < 0xffff; format_id++)
+    {
+        SetLastError(0xdeadbeef);
+        len = GetClipboardFormatNameA(format_id, buf, 256);
+
+        if (format_id < 0xc000)
+        {
+            ok(!len, "GetClipboardFormatNameA should fail, but it returned %d (%s)\n", len, buf);
+            test_last_error(ERROR_INVALID_PARAMETER);
+        }
+        else
+        {
+            if (len)
+                trace("%04x: %s\n", format_id, len ? buf : "");
+            else
+                test_last_error(ERROR_INVALID_HANDLE);
+        }
+    }
+#endif
+
+    ok(OpenClipboard(0), "OpenClipboard error %ld\n", GetLastError());
+
+    trace("# of formats available: %d\n", CountClipboardFormats());
+
+    format_id = 0;
+    while ((format_id = EnumClipboardFormats(format_id)))
+    {
+        ok(IsClipboardFormatAvailable(format_id), "format %04x was listed as available\n", format_id);
+        len = GetClipboardFormatNameA(format_id, buf, 256);
+        trace("%04x: %s\n", format_id, len ? buf : "");
+    }
+
+    ok(EmptyClipboard(), "EmptyClipboard error %ld\n", GetLastError());
+    ok(CloseClipboard(), "CloseClipboard error %ld\n", GetLastError());
+
+    if (CountClipboardFormats())
+    {
+        SetLastError(0xdeadbeef);
+        ok(!EnumClipboardFormats(0), "EnumClipboardFormats should fail if clipboard wasn't open\n");
+        ok(GetLastError() == ERROR_CLIPBOARD_NOT_OPEN,
+           "Last error should be set to ERROR_CLIPBOARD_NOT_OPEN, not %ld\n", GetLastError());
+    }
+
+    SetLastError(0xdeadbeef);
+    ok(!EmptyClipboard(), "EmptyClipboard should fail if clipboard wasn't open\n");
+    test_last_error(ERROR_CLIPBOARD_NOT_OPEN);
+}
+
+START_TEST(clipboard)
+{
+    SetLastError(0xdeadbeef);
+    FindAtomW(NULL);
+    if (GetLastError() == ERROR_CALL_NOT_IMPLEMENTED) is_win9x = TRUE;
+
+    test_RegisterClipboardFormatA();
+    test_ClipboardOwner();
+}
diff --git a/dlls/x11drv/clipboard.c b/dlls/x11drv/clipboard.c
index 5dbb9e1..c43ccd9 100644
--- a/dlls/x11drv/clipboard.c
+++ b/dlls/x11drv/clipboard.c
@@ -2038,24 +2038,30 @@
  */
 INT X11DRV_GetClipboardFormatName(UINT wFormat, LPSTR retStr, INT maxlen)
 {
-    INT len = 0;
-    LPWINE_CLIPFORMAT lpFormat = X11DRV_CLIPBOARD_LookupFormat(wFormat);
+    INT len;
+    LPWINE_CLIPFORMAT lpFormat;
 
     TRACE("(%04X, %p, %d) !\n", wFormat, retStr, maxlen);
 
+    if (wFormat < 0xc000)
+    {
+        SetLastError(ERROR_INVALID_PARAMETER);
+        return 0;
+    }
+
+    lpFormat = X11DRV_CLIPBOARD_LookupFormat(wFormat);
+
     if (!lpFormat || (lpFormat->wFlags & CF_FLAG_BUILTINFMT))
     {
         TRACE("Unknown format 0x%08x!\n", wFormat);
-        SetLastError(ERROR_INVALID_PARAMETER);
-    }
-    else
-    {
-        strncpy(retStr, lpFormat->Name, maxlen - 1);
-        retStr[maxlen - 1] = 0;
-
-        len = strlen(retStr);
+        SetLastError(ERROR_INVALID_HANDLE);
+        return 0;
     }
 
+    strncpy(retStr, lpFormat->Name, maxlen - 1);
+    retStr[maxlen - 1] = 0;
+
+    len = strlen(retStr);
     return len;
 }