diff --git a/src/pkcs11/pkcs11-opensc.h b/src/pkcs11/pkcs11-opensc.h
index 33beb6a3..6f0954dd 100644
--- a/src/pkcs11/pkcs11-opensc.h
+++ b/src/pkcs11/pkcs11-opensc.h
@@ -2,13 +2,22 @@
 #define PKCS11_OPENSC_H
 
 /* OpenSC specific extensions */
+/*
+ * define OpenSC specific Vendor Defined  extensions
+ * to make unique OpenSC  flags, attribures, mechanisms, etc.
+ * 
+ * Netscape used NSSCK_VENDOR_NSS 0x4E534350 "NSCP"
+ */
+
+#define SC_VENDOR_DEFINED 0x4F534300  /* OSC */
+
 /*
  * In PKCS#11 there is no CKA_ attribute dedicated to the NON-REPUDIATION flag.
  * We need this flag in PKCS#15/libopensc to make dinstinction between
  * 'signature' and 'qualified signature' key slots.
  */
-#define CKA_OPENSC_NON_REPUDIATION      (CKA_VENDOR_DEFINED | 1UL)
+#define CKA_OPENSC_NON_REPUDIATION      (CKA_VENDOR_DEFINED | SC_VENDOR_DEFINED | 1UL)
 
-#define CKA_SPKI			(CKA_VENDOR_DEFINED | 2UL)
+#define CKA_SPKI			(CKA_VENDOR_DEFINED | SC_VENDOR_DEFINED | 2UL)
 
 #endif