diff --git a/gost3411-2012-core.h b/gost3411-2012-core.h

index 67b5d4d..811be04 100644

--- a/gost3411-2012-core.h

+++ b/gost3411-2012-core.h

@@ -25,7 +25,7 @@

 #include "gost3411-2012-ref.h"

 #endif

-ALIGN(16) union uint512_u

+ALIGN(16) extern union uint512_u

 {

     unsigned long long QWORD[8];

 } uint512_u;