diff --git a/sources/system/unix-date-interface.dylan b/sources/system/unix-date-interface.dylan
index 6ecefeb146..b0ff367a7c 100644
--- a/sources/system/unix-date-interface.dylan
+++ b/sources/system/unix-date-interface.dylan
@@ -109,7 +109,7 @@ define method native-clock-to-tm (time :: <machine-word>) => (tm :: <machine-wor
       := primitive-unwrap-machine-word(time);
     let tm = primitive-wrap-machine-word
                (primitive-cast-pointer-as-raw
-		  (%call-c-function ("localtime")
+		  (%call-c-function ("system_localtime")
 		       (time :: <raw-c-pointer>) => (tm :: <raw-c-pointer>)
 		     (primitive-cast-raw-as-pointer(primitive-unwrap-machine-word(timeloc)))
 		   end));
diff --git a/sources/system/unix-portability.c b/sources/system/unix-portability.c
index 9cfda12bb9..d423d8c1f8 100644
--- a/sources/system/unix-portability.c
+++ b/sources/system/unix-portability.c
@@ -2,6 +2,7 @@
 #include <signal.h>
 #include <errno.h>
 #include <dlfcn.h>
+#include <time.h>
 
 #ifdef __APPLE__
 #include <crt_externs.h>
@@ -15,6 +16,12 @@ char **system_environ(void)
   return environ;
 }
 
+struct tm *system_localtime(const time_t *timep)
+{
+  struct tm *res = GC_malloc(sizeof(struct tm));
+  return localtime_r(timep, res);
+}
+
 /* Adapted from the SBCL run-time system, which in turn is derived
  * from the CMU CL system, which was written at Carnegie Mellon
  * University and released into the public domain.