diff --git a/libc/private/bionic_time_conversions.h b/libc/private/bionic_time_conversions.h
index fb049f2..c6b3c78 100644
--- a/libc/private/bionic_time_conversions.h
+++ b/libc/private/bionic_time_conversions.h
@@ -45,6 +45,9 @@
 __LIBC_HIDDEN__ void monotonic_time_from_realtime_time(timespec& monotonic_time,
                                                        const timespec& realtime_time);
 
+__LIBC_HIDDEN__ void realtime_time_from_monotonic_time(timespec& realtime_time,
+                                                       const timespec& monotonic_time);
+
 __END_DECLS
 
 static inline int check_timespec(const timespec* ts, bool null_allowed) {