diff --git a/base/Base_compiler.jl b/base/Base_compiler.jl
index a10a36bfc7767..03c1139906aad 100644
--- a/base/Base_compiler.jl
+++ b/base/Base_compiler.jl
@@ -160,7 +160,7 @@ end
 
 Get the time in nanoseconds relative to some machine-specific arbitrary time in the past.
 The primary use is for measuring elapsed times during program execution.  The return value is guaranteed to
-be monotonic while the system is running, and is unaffected by clock drift or changes to local calendar time,
+be monotonic (mod 2⁶⁴) while the system is running, and is unaffected by clock drift or changes to local calendar time,
 but it may change arbitrarily across system reboots or suspensions.
 
 (Although the returned time is always in nanoseconds, the timing resolution is platform-dependent.)