diff --git a/libc/include/sys/time.h b/libc/include/sys/time.h
index 4dee4da..1f010d4 100644
--- a/libc/include/sys/time.h
+++ b/libc/include/sys/time.h
@@ -56,7 +56,7 @@
 #define timeradd(a, b, res)                           \
     do {                                              \
         (res)->tv_sec  = (a)->tv_sec  + (b)->tv_sec;  \
-        (res)->tv_usec = (a)->tv_usec - (b)->tv_usec; \
+        (res)->tv_usec = (a)->tv_usec + (b)->tv_usec; \
         if ((res)->tv_usec >= 1000000) {              \
             (res)->tv_usec -= 1000000;                \
             (res)->tv_sec  += 1;                      \