diff --git a/sdk/head/units.h b/sdk/head/units.h
index b726163..91083c1 100644
--- a/sdk/head/units.h
+++ b/sdk/head/units.h
@@ -18,6 +18,7 @@
 #define FSEC_PER_SECOND 1000000000000000ULL
 #define NSEC_PER_SECOND 1000000000ULL
 #define USEC_PER_SECOND 1000000ULL
+#define USEC_PER_MSEC   1000ULL
 
 /* Frequency units */
 #define HZ_PER_MHZ 1000000