no longer supported starting C++17
diff --git a/lib/common/bitstream.h b/lib/common/bitstream.h
index 2094823..fcf3843 100644
--- a/lib/common/bitstream.h
+++ b/lib/common/bitstream.h
@@ -167,7 +167,7 @@
 /*-**************************************************************
 *  Internal functions
 ****************************************************************/
-MEM_STATIC unsigned BIT_highbit32 (register U32 val)
+MEM_STATIC unsigned BIT_highbit32 (U32 val)
 {
     assert(val != 0);
     {