diff --git a/src/vim.h b/src/vim.h
index 86d677b..8ae6856 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1943,6 +1943,11 @@
  #pragma option -p.
 #endif
 
+#ifdef _MSC_VER
+/* Avoid useless warning "conversion from X to Y of greater size". */
+ #pragma warning(disable : 4312)
+#endif
+
 #if defined(MEM_PROFILE)
 # define vim_realloc(ptr, size)  mem_realloc((ptr), (size))
 #else