diff --git a/libc/time/clock.cpp b/libc/time/clock.cpp
index 1b417188..fcd5111c 100644
--- a/libc/time/clock.cpp
+++ b/libc/time/clock.cpp
@@ -22,6 +22,7 @@
 
 *******************************************************************************/
 
+#include <assert.h>
 #include <time.h>
 
 // TODO: This function is crap and has been replaced by clock_gettime.