diff --git a/dlls/dwmapi/dwmapi.spec b/dlls/dwmapi/dwmapi.spec
index 8e01cacc6a5..8f8f7a31cbf 100644
--- a/dlls/dwmapi/dwmapi.spec
+++ b/dlls/dwmapi/dwmapi.spec
@@ -36,7 +36,7 @@
 @ stdcall DwmIsCompositionEnabled(ptr)
 @ stub DwmModifyPreviousDxFrameDuration
 @ stub DwmQueryThumbnailSourceSize
-@ stub DwmRegisterThumbnail
+@ stdcall DwmRegisterThumbnail(long long ptr)
 @ stub DwmSetDxFrameDuration
 @ stub DwmSetPresentParameters
 @ stdcall DwmSetWindowAttribute(long long ptr long)
diff --git a/dlls/dwmapi/dwmapi_main.c b/dlls/dwmapi/dwmapi_main.c
index c1bc0008565..39a99188a06 100644
--- a/dlls/dwmapi/dwmapi_main.c
+++ b/dlls/dwmapi/dwmapi_main.c
@@ -198,3 +198,13 @@ HRESULT WINAPI DwmGetWindowAttribute(HWND hwnd, DWORD attribute, PVOID pv_attrib
 
     return E_NOTIMPL;
 }
+
+/**********************************************************************
+ *           DwmRegisterThumbnail         (DWMAPI.@)
+ */
+HRESULT WINAPI DwmRegisterThumbnail(HWND dest, HWND src, PHTHUMBNAIL thumbnail_id)
+{
+    FIXME("(%p %p %p) stub\n", dest, src, thumbnail_id);
+
+    return E_NOTIMPL;
+}
diff --git a/include/dwmapi.h b/include/dwmapi.h
index ecc515c3de9..b2546ae0201 100644
--- a/include/dwmapi.h
+++ b/include/dwmapi.h
@@ -30,6 +30,7 @@ extern "C" {
 #endif
 
 DECLARE_HANDLE(HTHUMBNAIL);
+typedef HTHUMBNAIL *PHTHUMBNAIL;
 
 typedef struct _MilMatrix3x2D
 {
@@ -60,6 +61,7 @@ DWMAPI DwmEnableMMCSS(BOOL);
 DWMAPI DwmExtendFrameIntoClientArea(HWND,const MARGINS*);
 DWMAPI DwmGetColorizationColor(DWORD*,BOOL);
 DWMAPI DwmIsCompositionEnabled(BOOL*);
+DWMAPI DwmRegisterThumbnail(HWND, HWND, PHTHUMBNAIL);
 DWMAPI DwmSetWindowAttribute(HWND, DWORD, LPCVOID, DWORD);
 DWMAPI DwmUnregisterThumbnail(HTHUMBNAIL);