diff --git a/src/base/abci/abc.c b/src/base/abci/abc.c
index 6896f5b15..e019d8104 100644
--- a/src/base/abci/abc.c
+++ b/src/base/abci/abc.c
@@ -63,6 +63,7 @@
 #include "opt/fret/fretime.h"
 #include "opt/nwk/nwkMerge.h"
 #include "base/acb/acbPar.h"
+#include "misc/extra/extra.h"
 
 
 #ifndef _WIN32
@@ -603,6 +604,8 @@ extern Abc_Ntk_t * Abc_NtkFromAigPhase( Aig_Man_t * pMan );
 extern Vec_Ptr_t * Abc_NtkCollectCiNames( Abc_Ntk_t * pNtk );
 extern Vec_Ptr_t * Abc_NtkCollectCoNames( Abc_Ntk_t * pNtk );
 
+extern void Extra_BitMatrixTransposeP( Vec_Wrd_t * vSimsIn, int nWordsIn, Vec_Wrd_t * vSimsOut, int nWordsOut );
+
 ////////////////////////////////////////////////////////////////////////
 ///                     FUNCTION DEFINITIONS                         ///
 ////////////////////////////////////////////////////////////////////////
@@ -34013,7 +34016,6 @@ int Abc_CommandAbc9WriteSim( Abc_Frame_t * pAbc, int argc, char ** argv )
     }
     if ( fOutputs )
     {
-        extern void Extra_BitMatrixTransposeP( Vec_Wrd_t * vSimsIn, int nWordsIn, Vec_Wrd_t * vSimsOut, int nWordsOut );
         Vec_Wrd_t * vTemp;
         assert( Vec_WrdSize(pAbc->pGia->vSimsPo) % Gia_ManCoNum(pAbc->pGia) == 0 );
         if ( fTrans )