--- CHANGES.md.orig	2024-09-10 00:00:00.000000000 +0000
+++ CHANGES.md	2026-03-03 10:00:05.000000000 +0100
@@ -1,3 +1,10 @@
+
+
+- `Mtime_clock`. Restore compatiblity with MacOS < 10.12. Before 10.12
+  we use `mach_absolute_time` instead of `mach_continuous_time` which
+  means that sleep time is not taken into account. Thanks to
+  Sergey Fedorov for the report and help (#51).
+
 v2.1.0 2024-09-10 Zagreb
 ------------------------
 
--- src/clock/mtime_clock.mli.orig	2024-09-10 00:00:00.000000000 +0000
+++ src/clock/mtime_clock.mli	2026-03-03 10:00:05.000000000 +0100
@@ -89,9 +89,10 @@
     {- Platforms with a POSIX clock use
        {{:http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_gettime.html}[clock_gettime]}
        with CLOCK_MONOTONIC.}
-    {- Darwin uses
-       {{:https://developer.apple.com/documentation/kernel/1646199-mach_continuous_time}[mach_continous_time]}.
-       This means that sleep time is taken into account.}
+    {- MacOS >= 10.12 uses
+       {{:https://developer.apple.com/documentation/kernel/1646199-mach_continuous_time}[mach_continous_time]}, sleep time is taken into
+       account. For MacOS < 10.12, {{:https://developer.apple.com/documentation/kernel/1462446-mach_absolute_time}[mach_absolute_time]} is used, sleep time
+       is not taken into account.}
     {- Windows uses
        {{:https://msdn.microsoft.com/en-us/library/windows/desktop/aa373083%28v=vs.85%29.aspx}Performance counters}. }
     {- JavaScript uses
--- src/clock/mtime_clock_stubs.c.orig	2024-09-10 00:00:00.000000000 +0000
+++ src/clock/mtime_clock_stubs.c	2026-03-03 10:00:05.000000000 +0100
@@ -19,7 +19,6 @@
 
 #if defined(__APPLE__) && defined(__MACH__)
   #define OCAML_MTIME_DARWIN
-
 #elif defined(__unix__) || defined(__unix)
  #include <unistd.h>
  #if defined(__linux__)
@@ -38,6 +37,14 @@
 
 #include <mach/mach_time.h>
 
+#include <AvailabilityMacros.h>
+
+#if MAC_OS_X_VERSION_MIN_REQUIRED >= 101200
+  #define ocaml_darwin_mach_time mach_continuous_time
+#else
+  #define ocaml_darwin_mach_time mach_absolute_time
+#endif
+
 static mach_timebase_info_data_t scale = {0};
 
 void ocaml_mtime_clock_init_scale (void)
@@ -52,9 +58,9 @@
 CAMLprim value ocaml_mtime_clock_elapsed_ns (value unit)
 {
   static uint64_t start = 0L;
-  if (start == 0L) { start = mach_continuous_time (); }
+  if (start == 0L) { start = ocaml_darwin_mach_time (); }
   if (scale.denom == 0) { ocaml_mtime_clock_init_scale (); }
-  uint64_t now = mach_continuous_time ();
+  uint64_t now = ocaml_darwin_mach_time ();
   return caml_copy_int64 (((now - start) * scale.numer) / scale.denom);
 }
 
@@ -62,7 +68,7 @@
 CAMLprim value ocaml_mtime_clock_now_ns (value unit)
 {
   if (scale.denom == 0) { ocaml_mtime_clock_init_scale (); }
-  uint64_t now = mach_continuous_time ();
+  uint64_t now = ocaml_darwin_mach_time ();
   return caml_copy_int64 ((now * scale.numer) / scale.denom);
 }