diff --git a/src/gen_dispatch.py b/src/gen_dispatch.py
index faa55da..b686824 100755
--- a/src/gen_dispatch.py
+++ b/src/gen_dispatch.py
@@ -516,9 +516,17 @@ class Generator(object):
             self.outln('typedef uint32_t khronos_uint32_t;')
             self.outln('typedef uint64_t khronos_uint64_t;')
             self.outln('typedef float khronos_float_t;')
-            self.outln('typedef long khronos_intptr_t;')
-            self.outln('typedef long khronos_ssize_t;')
-            self.outln('typedef unsigned long khronos_usize_t;')
+            self.outln('#ifdef _WIN64')
+            self.outln('typedef signed   long long int khronos_intptr_t;')
+            self.outln('typedef unsigned long long int khronos_uintptr_t;')
+            self.outln('typedef signed   long long int khronos_ssize_t;')
+            self.outln('typedef unsigned long long int khronos_usize_t;')
+            self.outln('#else')
+            self.outln('typedef signed   long int      khronos_intptr_t;')
+            self.outln('typedef unsigned long int      khronos_uintptr_t;')
+            self.outln('typedef signed   long int      khronos_ssize_t;')
+            self.outln('typedef unsigned long int      khronos_usize_t;')
+            self.outln('#endif')
             self.outln('typedef uint64_t khronos_utime_nanoseconds_t;')
             self.outln('typedef int64_t khronos_stime_nanoseconds_t;')
             self.outln('#define KHRONOS_MAX_ENUM 0x7FFFFFFF')