diff --git a/libc/bionic/clock.cpp b/libc/bionic/clock.cpp
index 98f71af..a2636c6 100644
--- a/libc/bionic/clock.cpp
+++ b/libc/bionic/clock.cpp
@@ -34,5 +34,8 @@
 clock_t clock() {
   tms t;
   times(&t);
+  // Although times(2) and clock(3) both use the type clock_t, the units are
+  // different. For times(2) it's pure clock ticks, but for clock(3) the unit
+  // is CLOCKS_PER_SEC, so we need to scale appropriately.
   return (t.tms_utime + t.tms_stime) * (CLOCKS_PER_SEC / sysconf(_SC_CLK_TCK));
 }