diff --git a/src/pdumper.c b/src/pdumper.c
index c888b659dde..c0b36b1ca44 100644
--- a/src/pdumper.c
+++ b/src/pdumper.c
@@ -4853,11 +4853,14 @@ struct dump_memory_map_heap_control_block
 static void
 dump_mm_heap_cb_release (struct dump_memory_map_heap_control_block *cb)
 {
-  eassert (cb->refcount > 0);
-  if (--cb->refcount == 0)
+  if (cb)
     {
-      free (cb->mem);
-      free (cb);
+      eassert (cb->refcount > 0);
+      if (--cb->refcount == 0)
+	{
+	  free (cb->mem);
+	  free (cb);
+	}
     }
 }
 
diff --git a/src/w32dwrite.c b/src/w32dwrite.c
index 32e2644af2c..29f9d5f1fed 100644
--- a/src/w32dwrite.c
+++ b/src/w32dwrite.c
@@ -37,7 +37,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include <math.h>
 #include <windows.h>
 
-#ifndef MINGW_W64
+#if !defined MINGW_W64 && !defined CYGWIN
 # define INITGUID
 #endif
 #include <initguid.h>
@@ -659,7 +659,7 @@ w32_dwrite_encode_char (struct font *font, int c)
   if (dwrite_font_face == NULL)
     return FONT_INVALID_CODE;
   hr = dwrite_font_face->lpVtbl->GetGlyphIndices (dwrite_font_face,
-						  &c, 1, &index);
+						  (UINT32 *) &c, 1, &index);
   if (verify_hr (hr, "Failed to GetGlyphIndices"))
     {
       if (index == 0)
diff --git a/src/w32menu.c b/src/w32menu.c
index c3d147841b6..b5f87ebb42c 100644
--- a/src/w32menu.c
+++ b/src/w32menu.c
@@ -186,6 +186,11 @@ task_dialog_callback (HWND hwnd, UINT msg, WPARAM wParam,
 Lisp_Object
 w32_popup_dialog (struct frame *f, Lisp_Object header, Lisp_Object contents)
 {
+#ifdef NTGUI_UNICODE
+  typedef int (WINAPI *WideCharToMultiByte_Proc)(UINT,DWORD,LPCWSTR,int,LPSTR,
+						 int,LPCSTR,LPBOOL);
+  static MultiByteToWideChar_Proc pMultiByteToWideChar = MultiByteToWideChar;
+#endif /* NTGUI_UNICODE */
   check_window_system (f);
 
   if (task_dialog_indirect)