diff --git a/src/vim.h b/src/vim.h
index 111723f..87a80b8 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -352,8 +352,8 @@
 typedef unsigned short	short_u;
 typedef unsigned int	int_u;
 /* Make sure long_u is big enough to hold a pointer.
- * On Win64 longs are 32 bit and pointers 64 bit.
- * For printf() and scanf() we need to take care of long_u specifically. */
+ * On Win64, longs are 32 bits and pointers are 64 bits.
+ * For printf() and scanf(), we need to take care of long_u specifically. */
 #ifdef _WIN64
 typedef unsigned __int64        long_u;
 typedef		 __int64        long_i;
@@ -361,8 +361,16 @@
 # define SCANF_DECIMAL_LONG_U   "%Iu"
 # define PRINTF_HEX_LONG_U      "0x%Ix"
 #else
-typedef unsigned long	        long_u;
-typedef		 long	        long_i;
+  /* Microsoft-specific. The __w64 keyword should be specified on any typedefs
+   * that change size between 32-bit and 64-bit platforms.  For any such type,
+   * __w64 should appear only on the 32-bit definition of the typedef.
+   * Define __w64 as an empty token for everything but MSVC 7.x or later.
+   */
+# if !defined(_MSC_VER)	|| (_MSC_VER < 1300)
+#  define __w64 
+# endif
+typedef unsigned long __w64	long_u;
+typedef		 long __w64     long_i;
 # define SCANF_HEX_LONG_U       "%lx"
 # define SCANF_DECIMAL_LONG_U   "%lu"
 # define PRINTF_HEX_LONG_U      "0x%lx"