diff --git a/lib/c/labcomm_compat_vxworks.h b/lib/c/labcomm_compat_vxworks.h
index c5c1572eca289fe2a5baa4d72145a33c9bc2791e..ab32a5025c28d3a51c551f234291441ee9ebf7df 100644
--- a/lib/c/labcomm_compat_vxworks.h
+++ b/lib/c/labcomm_compat_vxworks.h
@@ -10,6 +10,7 @@
 #include <types.h>
 #include <timers.h>
 #include <stdio.h>
+#include <private/stdioP.h>
 
 #ifdef __INT64_MAX__
 #undef INT64_MAX
@@ -24,5 +25,6 @@
   #undef _BIG_ENDIAN
 #endif
 
-#endif
+extern unsigned int cpuFrequency;
 
+#endif