diff --git a/modules/libcom/src/osi/os/vxWorks/osdThread.h b/modules/libcom/src/osi/os/vxWorks/osdThread.h
index 259d358e5..25cce37ac 100644
--- a/modules/libcom/src/osi/os/vxWorks/osdThread.h
+++ b/modules/libcom/src/osi/os/vxWorks/osdThread.h
@@ -1,5 +1,5 @@
 /*************************************************************************\
-* Copyright (c) 2002 The University of Chicago, as Operator of Argonne
+* Copyright (c) 2021 The University of Chicago, as Operator of Argonne
 *     National Laboratory.
 * Copyright (c) 2002 The Regents of the University of California, as
 *     Operator of Los Alamos National Laboratory.
@@ -8,13 +8,22 @@
 * in file LICENSE that is included with this distribution.
 \*************************************************************************/
 
-#ifndef osdThreadh
-#define osdThreadh
+#ifndef INC_osdThread_H
+#define INC_osdThread_H
 
-/* VxWorks 6.9 and later can support joining threads */
+#include <epicsVersion.h>
 
-#if (_WRS_VXWORKS_MAJOR == 6 && _WRS_VXWORKS_MINOR < 9)
-#undef EPICS_THREAD_CAN_JOIN
+#ifdef _WRS_VXWORKS_MAJOR
+#  define VXWORKS_VERSION_INT VERSION_INT(_WRS_VXWORKS_MAJOR, \
+        _WRS_VXWORKS_MINOR, _WRS_VXWORKS_MAINT, _WRS_VXWORKS_SVCPK)
+#else
+/* Version not available at compile-time, assume... */
+#  define VXWORKS_VERSION_INT VERSION_INT(5, 5, 0, 0)
 #endif
 
-#endif /* osdThreadh */
+#if VXWORKS_VERSION_INT < VERSION_INT(6, 9, 4, 1)
+/* VxWorks 6.9.4.1 and later can support joining threads */
+#  undef EPICS_THREAD_CAN_JOIN
+#endif
+
+#endif /* INC_osdThread_H */