--- coregrind/m_libcproc.c.orig
+++ coregrind/m_libcproc.c
@@ -1033,6 +1033,13 @@ void VG_(flush_dcache) ( void *ptr, SizeT nbytes )
 #  endif
 }
 
+#if defined(__OpenBSD__)
+void VG_(__set_tcb)(void *tcb)
+{
+   (void)VG_(do_syscall1)(__NR___set_tcb, tcb);
+}
+#endif
+
 /*--------------------------------------------------------------------*/
 /*--- end                                                          ---*/
 /*--------------------------------------------------------------------*/
