diff --git a/ykcs11/pkcs11.h b/ykcs11/pkcs11.h
index 3d7e166..53b8df4 100644
--- a/ykcs11/pkcs11.h
+++ b/ykcs11/pkcs11.h
@@ -239,6 +239,9 @@ extern "C" {
 
 #define __PASTE(x,y)      x##y
 
+#if defined _WIN32 || _WIN64
+#pragma pack(push, cryptoki, 1)
+#endif
 
 /* packing defines */
 //#include "pkcs11p.h" // TODO: msc specific?
@@ -309,6 +312,11 @@ struct CK_FUNCTION_LIST {
 /* unpack */
 //#include "pkcs11u.h" // TODO: msc specific?
 
+#if defined _WIN32 || _WIN64
+#pragma pack(pop, cryptoki)
+#endif
+
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/ykcs11/pkcs11t.h b/ykcs11/pkcs11t.h
index 4e0569c..e24b372 100644
--- a/ykcs11/pkcs11t.h
+++ b/ykcs11/pkcs11t.h
@@ -108,7 +108,9 @@ typedef CK_VOID_PTR CK_PTR CK_VOID_PTR_PTR;
 
 
 /* pack */
-//#include "pkcs11p.h" // TODO: msc specific?
+#if defined _WIN32 || _WIN64
+#pragma pack(push, cryptoki, 1)
+#endif
 
 typedef struct CK_VERSION {
   CK_BYTE       major;  /* integer portion of version number */
@@ -1182,9 +1184,6 @@ typedef CK_EXTRACT_PARAMS CK_PTR CK_EXTRACT_PARAMS_PTR;
 #define CKA_NETSCAPE_DB				0xD5A0DB00UL
 #define CKA_NETSCAPE_TRUST			0x80000001UL
 
-/* undo packing */
-//#include "pkcs11u.h" // TODO: msc specific?
-
 // YUBICO specific attributes
 #define CKA_TOUCH_PIN_DEFAULT 0x00000000U
 #define CKA_TOUCH_ALWAYS      0x00000001U
@@ -1193,4 +1192,9 @@ typedef CK_EXTRACT_PARAMS CK_PTR CK_EXTRACT_PARAMS_PTR;
 #define CKA_PIN_NEVER         0x00000008U
 #define CKA_TOUCH_NEVER       0x00000016U
 
+/* undo packing */
+#if defined _WIN32 || _WIN64
+#pragma pack(pop, cryptoki)
+#endif
+
 #endif