diff --git a/portable/MSVC-MingW/portmacro.h b/portable/MSVC-MingW/portmacro.h
index b1282b3d7..652792317 100644
--- a/portable/MSVC-MingW/portmacro.h
+++ b/portable/MSVC-MingW/portmacro.h
@@ -42,12 +42,19 @@
 #define portLONG        long
 #define portSHORT       short
 #define portSTACK_TYPE  size_t
-#define portBASE_TYPE   long
 #define portPOINTER_SIZE_TYPE size_t
 
 typedef portSTACK_TYPE StackType_t;
-typedef long BaseType_t;
-typedef unsigned long UBaseType_t;
+
+#if defined( __x86_64__) || defined( _M_X64 )
+    #define portBASE_TYPE   long long
+    typedef long long BaseType_t;
+    typedef unsigned long long UBaseType_t;
+#else
+    #define portBASE_TYPE   long
+    typedef long BaseType_t;
+    typedef unsigned long UBaseType_t;
+#endif
 
 
 #if( configTICK_TYPE_WIDTH_IN_BITS == TICK_TYPE_WIDTH_16_BITS )