diff --git a/win32ss/user/user32/misc/exticon.c b/win32ss/user/user32/misc/exticon.c
index ba2bd6d6b2c..c9781b44de0 100644
--- a/win32ss/user/user32/misc/exticon.c
+++ b/win32ss/user/user32/misc/exticon.c
@@ -447,14 +447,25 @@ static UINT ICO_ExtractIconExW(
                 {
                     HICON icon;
                     WORD *cursorData = NULL;
+                    BITMAPINFOHEADER bmih;
 
                     imageData = peimage + dataOffset;
                     entry = (LPICONIMAGE)(imageData);
 
+                    memcpy(&bmih, imageData, sizeof(BITMAPINFOHEADER));
                     if(sig == 2)
                     {
+                         /* biSizeImage is the size of the raw bitmap data.
+                          * A dummy 0 can be given for BI_RGB bitmaps.
+                          * https://en.wikipedia.org/wiki/BMP_file_format */
+                         if ((bmih.biCompression == BI_RGB) &&
+                             (entry->icHeader.biSizeImage == 0))
+                         {
+                             bmih.biSizeImage = bmih.biWidth *
+                                 bmih.biHeight / 2 * bmih.biBitCount / 8;
+                         }
                         /* we need to prepend the bitmap data with hot spots for CreateIconFromResourceEx */
-                        cursorData = HeapAlloc(GetProcessHeap(), 0, entry->icHeader.biSizeImage + 2 * sizeof(WORD));
+                        cursorData = HeapAlloc(GetProcessHeap(), 0, bmih.biSizeImage + 2 * sizeof(WORD));
 
                         if(!cursorData)
                             continue;
@@ -462,12 +473,12 @@ static UINT ICO_ExtractIconExW(
                         cursorData[0] = hotSpot.x;
                         cursorData[1] = hotSpot.y;
 
-                        memcpy(cursorData + 2, imageData, entry->icHeader.biSizeImage);
+                        memcpy(cursorData + 2, imageData, bmih.biSizeImage);
 
                         imageData = (LPBYTE)cursorData;
                     }
 
-                    icon = CreateIconFromResourceEx(imageData, entry->icHeader.biSizeImage, sig == 1, 0x00030000, cx[index], cy[index], flags);
+                    icon = CreateIconFromResourceEx(imageData, bmih.biSizeImage, sig == 1, 0x00030000, cx[index], cy[index], flags);
 
                     HeapFree(GetProcessHeap(), 0, cursorData);