diff --git a/reactos/dll/win32/user32/include/user32p.h b/reactos/dll/win32/user32/include/user32p.h
index 182068413f1..4dec7cbd1f4 100644
--- a/reactos/dll/win32/user32/include/user32p.h
+++ b/reactos/dll/win32/user32/include/user32p.h
@@ -76,6 +76,9 @@
 #define NtUserSetCaretBlinkTime(uMSeconds) \
   (BOOL)NtUserCallOneParam((DWORD)uMSeconds, ONEPARAM_ROUTINE_SETCARETBLINKTIME)
 
+#define NtUserRegisterUserModule(hInstance) \
+  (BOOL)NtUserCallOneParam((DWORD)hInstance, ONEPARAM_ROUTINE_REGISTERUSERMODULE)
+
 /*
 #define NtUserEnumClipboardFormats(format) \
   (UINT)NtUserCallOneParam(format, ONEPARAM_ROUTINE_ENUMCLIPBOARDFORMATS)
diff --git a/reactos/dll/win32/user32/misc/dllmain.c b/reactos/dll/win32/user32/misc/dllmain.c
index 41b40d88438..f37b36b66e9 100644
--- a/reactos/dll/win32/user32/misc/dllmain.c
+++ b/reactos/dll/win32/user32/misc/dllmain.c
@@ -93,6 +93,9 @@ DllMain(
    {
       case DLL_PROCESS_ATTACH:
          User32Instance = hInstanceDll;
+         if (!NtUserRegisterUserModule(hInstanceDll))
+             return FALSE;
+
          hProcessHeap = RtlGetProcessHeap();
          if (!Init())
             return FALSE;
diff --git a/reactos/include/reactos/win32k/ntuser.h b/reactos/include/reactos/win32k/ntuser.h
index 150d8c94ae5..ed7c1f2118f 100644
--- a/reactos/include/reactos/win32k/ntuser.h
+++ b/reactos/include/reactos/win32k/ntuser.h
@@ -60,6 +60,7 @@ typedef struct _WINDOWCLASS
 typedef struct _W32PROCESSINFO
 {
     PVOID UserHandleTable;
+    HINSTANCE hModUser;
     PWINDOWCLASS LocalClassList;
     PWINDOWCLASS GlobalClassList;
     PWINDOWCLASS SystemClassList;
@@ -458,7 +459,8 @@ NtUserCallNoParam(
 #define ONEPARAM_ROUTINE_MSQSETWAKEMASK       0x27
 #define ONEPARAM_ROUTINE_GETKEYBOARDTYPE      0x28
 #define ONEPARAM_ROUTINE_GETKEYBOARDLAYOUT    0x29
-#define ONEPARAM_ROUTINE_SHOWCURSOR           0x30 
+#define ONEPARAM_ROUTINE_SHOWCURSOR           0x30
+#define ONEPARAM_ROUTINE_REGISTERUSERMODULE   0x31
 DWORD
 NTAPI
 NtUserCallOneParam(
diff --git a/reactos/subsystems/win32/win32k/ntuser/class.c b/reactos/subsystems/win32/win32k/ntuser/class.c
index 9ade435dec3..41ecd39255b 100644
--- a/reactos/subsystems/win32/win32k/ntuser/class.c
+++ b/reactos/subsystems/win32/win32k/ntuser/class.c
@@ -592,7 +592,7 @@ IntDereferenceClass(IN OUT PWINDOWCLASS Class,
 
                 while (*PrevLink != BaseClass)
                 {
-                    ASSERT(BaseClass != NULL);
+                    ASSERT(*PrevLink != NULL);
                     PrevLink = &BaseClass->Next;
                 }
 
@@ -1112,7 +1112,27 @@ IntGetClassAtom(IN PUNICODE_STRING ClassName,
             goto FoundClass;
         }
 
-        /* Step 3: try to find a system class */
+        /* Step 3: try to find any local class registered by user32 */
+        Class = IntFindClass(Atom,
+                             pi->hModUser,
+                             &pi->LocalClassList,
+                             Link);
+        if (Class != NULL)
+        {
+            goto FoundClass;
+        }
+
+        /* Step 4: try to find any global class registered by user32 */
+        Class = IntFindClass(Atom,
+                             pi->hModUser,
+                             &pi->GlobalClassList,
+                             Link);
+        if (Class != NULL)
+        {
+            goto FoundClass;
+        }
+
+        /* Step 5: try to find a system class */
         Class = IntFindClass(Atom,
                              NULL,
                              &pi->SystemClassList,
@@ -1771,10 +1791,13 @@ UserGetClassInfo(IN PWINDOWCLASS Class,
                  IN BOOL Ansi,
                  HINSTANCE hInstance)
 {
+    PW32PROCESSINFO pi;
+
     lpwcx->style = Class->Style;
 
+    pi = GetW32ProcessInfo();
     lpwcx->lpfnWndProc = IntGetClassWndProc(Class,
-                                            GetW32ProcessInfo(),
+                                            pi,
                                             Ansi,
                                             FALSE);
 
@@ -1789,9 +1812,7 @@ UserGetClassInfo(IN PWINDOWCLASS Class,
     else
         lpwcx->lpszMenuName = Class->MenuName;
 
-    if (hInstance)
-        lpwcx->hInstance = hInstance;
-    else if (Class->Global)
+    if (Class->hInstance == pi->hModUser)
         lpwcx->hInstance = NULL;
     else
         lpwcx->hInstance = Class->hInstance;
@@ -2119,7 +2140,7 @@ NtUserGetClassInfo(
         /* probe the paramters */
         CapturedClassName = ProbeForReadUnicodeString(ClassName);
 
-        if (IS_ATOM(CapturedClassName.Buffer))
+        if (CapturedClassName.Length == 0)
             TRACE("hInst %p atom %04X lpWndClassEx %p Ansi %d\n", hInstance, CapturedClassName.Buffer, lpWndClassEx, Ansi);
         else
             TRACE("hInst %p class %wZ lpWndClassEx %p Ansi %d\n", hInstance, &CapturedClassName, lpWndClassEx, Ansi);
@@ -2162,6 +2183,9 @@ InvalidParameter:
                                     NULL);
         if (ClassAtom != (RTL_ATOM)0)
         {
+            if (hInstance == NULL)
+                hInstance = pi->hModUser;
+
             Ret = UserGetClassInfo(Class,
                                    lpWndClassEx,
                                    Ansi,
@@ -2186,7 +2210,10 @@ InvalidParameter:
 
                 if (!(Class->Global || Class->System) && hInstance == NULL)
                 {
-                    WARN("Tried to get information of a non-existing class\n");
+                    if (CapturedClassName.Length == 0)
+                       WARN("Tried to get information of a non-existing class atom 0x%p\n", CapturedClassName.Buffer);
+                    else
+                       WARN("Tried to get information of a non-existing class \"%wZ\"\n", &CapturedClassName);
                     SetLastWin32Error(ERROR_CLASS_DOES_NOT_EXIST);
                     Ret = FALSE;
                 }
@@ -2194,7 +2221,10 @@ InvalidParameter:
          }
          else
          {
-            WARN("Tried to get information of a non-existing class\n");
+            if (CapturedClassName.Length == 0)
+               WARN("Tried to get information of a non-existing class atom 0x%p\n", CapturedClassName.Buffer);
+            else
+               WARN("Tried to get information of a non-existing class \"%wZ\"\n", &CapturedClassName);
             SetLastWin32Error(ERROR_CLASS_DOES_NOT_EXIST);
          }
     }
diff --git a/reactos/subsystems/win32/win32k/ntuser/misc.c b/reactos/subsystems/win32/win32k/ntuser/misc.c
index 019d61104be..38cf5d0bb83 100644
--- a/reactos/subsystems/win32/win32k/ntuser/misc.c
+++ b/reactos/subsystems/win32/win32k/ntuser/misc.c
@@ -407,6 +407,26 @@ NtUserCallOneParam(
 
       case ONEPARAM_ROUTINE_GETKEYBOARDLAYOUT:
          RETURN( (DWORD)UserGetKeyboardLayout(Param));
+
+      case ONEPARAM_ROUTINE_REGISTERUSERMODULE:
+      {
+          PW32THREADINFO ti;
+
+          ti = GetW32ThreadInfo();
+          if (ti == NULL)
+          {
+              DPRINT1("Cannot register user32 module instance!\n");
+              SetLastWin32Error(ERROR_INVALID_PARAMETER);
+              RETURN(FALSE);
+          }
+
+          if (InterlockedCompareExchangePointer(&ti->kpi->hModUser,
+                                                (HINSTANCE)Param,
+                                                NULL) == NULL)
+          {
+              RETURN(TRUE);
+          }
+      }
    }
    DPRINT1("Calling invalid routine number 0x%x in NtUserCallOneParam(), Param=0x%x\n",
            Routine, Param);