diff --git a/CMakeLists.txt b/CMakeLists.txt
index a67405a..03c87a4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -283,6 +283,12 @@ endif()
 if(WIN32)
 	set(OPENSSL_LIBS ${OPENSSL_LIBS} ws2_32)
 endif()
+
+check_function_exists(clock_gettime HAVE_CLOCK_GETTIME)
+if(HAVE_CLOCK_GETTIME)
+	add_definitions(-DHAVE_CLOCK_GETTIME)
+endif()
+
 if(CMAKE_SYSTEM_NAME MATCHES "Linux")
 	check_library_exists(rt clock_gettime "time.h" HAVE_CLOCK_GETTIME)
 	if (HAVE_CLOCK_GETTIME)
diff --git a/apps/openssl/Makefile.am b/apps/openssl/Makefile.am
index 9b9eb10..f100adb 100644
--- a/apps/openssl/Makefile.am
+++ b/apps/openssl/Makefile.am
@@ -74,6 +74,12 @@ openssl_SOURCES += compat/poll_win.c
 endif
 endif
 
+if !HAVE_CLOCK_GETTIME
+if HOST_DARWIN
+openssl_SOURCES += compat/clock_gettime_osx.c
+endif
+endif
+
 if !HAVE_STRTONUM
 openssl_SOURCES += compat/strtonum.c
 endif
diff --git a/apps/openssl/compat/clock_gettime_osx.c b/apps/openssl/compat/clock_gettime_osx.c
new file mode 100644
index 0000000..5545187
--- /dev/null
+++ b/apps/openssl/compat/clock_gettime_osx.c
@@ -0,0 +1,26 @@
+#include <time.h>
+
+#include <mach/mach_time.h>
+#define ORWL_NANO (+1.0E-9)
+#define ORWL_GIGA UINT64_C(1000000000)
+
+int
+clock_gettime(clockid_t clock_id, struct timespec *tp)
+{
+	static double orwl_timebase = 0.0;
+	static uint64_t orwl_timestart = 0;
+
+	if (!orwl_timestart) {
+		mach_timebase_info_data_t tb = { 0 };
+		mach_timebase_info(&tb);
+		orwl_timebase = tb.numer;
+		orwl_timebase /= tb.denom;
+		orwl_timestart = mach_absolute_time();
+	}
+
+	double diff = (mach_absolute_time() - orwl_timestart) * orwl_timebase;
+	tp->tv_sec = diff * ORWL_NANO;
+	tp->tv_nsec = diff - (tp->tv_sec * ORWL_GIGA);
+
+	return 0;
+}
diff --git a/include/compat/sys/time.h b/include/compat/sys/time.h
index 3d31985..76428c1 100644
--- a/include/compat/sys/time.h
+++ b/include/compat/sys/time.h
@@ -13,10 +13,6 @@ int gettimeofday(struct timeval *tp, void *tzp);
 #include_next <sys/time.h>
 #endif
 
-#ifndef CLOCK_MONOTONIC
-#define CLOCK_MONOTONIC CLOCK_REALTIME
-#endif
-
 #ifndef timersub
 #define timersub(tvp, uvp, vvp)                                         \
 	do {                                                            \
diff --git a/include/compat/time.h b/include/compat/time.h
index df65530..dc460ef 100644
--- a/include/compat/time.h
+++ b/include/compat/time.h
@@ -13,6 +13,9 @@
 #include_next <time.h>
 #endif
 
+#ifndef LIBCRYPTOCOMPAT_TIME_H
+#define LIBCRYPTOCOMPAT_TIME_H
+
 #ifdef _WIN32
 struct tm *__gmtime_r(const time_t * t, struct tm * tm);
 #define gmtime_r(tp, tm) __gmtime_r(tp, tm)
@@ -22,6 +25,19 @@ struct tm *__gmtime_r(const time_t * t, struct tm * tm);
 time_t timegm(struct tm *tm);
 #endif
 
+#ifndef CLOCK_MONOTONIC
+#define CLOCK_MONOTONIC CLOCK_REALTIME
+#endif
+
+#ifndef CLOCK_REALTIME
+#define CLOCK_REALTIME 0
+#endif
+
+#ifndef HAVE_CLOCK_GETTIME
+typedef int clockid_t;
+int clock_gettime(clockid_t clock_id, struct timespec *tp);
+#endif
+
 #ifndef timespecsub
 #define timespecsub(tsp, usp, vsp)                                      \
         do {                                                            \
@@ -33,3 +49,5 @@ time_t timegm(struct tm *tm);
                 }                                                       \
         } while (0)
 #endif
+
+#endif
diff --git a/m4/check-libc.m4 b/m4/check-libc.m4
index cacdd17..1fff77e 100644
--- a/m4/check-libc.m4
+++ b/m4/check-libc.m4
@@ -126,11 +126,13 @@ AM_CONDITIONAL([HAVE_ARC4RANDOM_BUF],
 	   -a "x$ac_cv_func_arc4random_buf" = xyes])
 
 # Check for getentropy fallback dependencies
-AC_CHECK_FUNC([getauxval])
-AC_SEARCH_LIBS([clock_gettime],[rt posix4])
-AC_CHECK_FUNC([clock_gettime])
+AC_CHECK_FUNCS([getauxval])
 AC_SEARCH_LIBS([dl_iterate_phdr],[dl])
-AC_CHECK_FUNC([dl_iterate_phdr])
+AC_CHECK_FUNCS([dl_iterate_phdr])
+
+AC_SEARCH_LIBS([clock_gettime],[rt posix4])
+AC_CHECK_FUNCS([clock_gettime])
+AM_CONDITIONAL([HAVE_CLOCK_GETTIME], [test "x$ac_cv_func_clock_gettime" = xyes])
 ])
 
 AC_DEFUN([CHECK_VA_COPY], [