--- a/lib/execute.c	(index)
+++ b/lib/execute.c	(working tree)
@@ -48,6 +48,9 @@
 
 #endif
 
+#if defined(__FreeBSD__) || defined(__MACH__)
+    extern char** environ;
+#endif
 
 #if defined EINTR && ((defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__)
 
--- a/lib/spawn-pipe.c	(index)
+++ b/lib/spawn-pipe.c	(working tree)
@@ -53,7 +53,10 @@
 # include <spawn.h>

 #endif
 
+#if defined(__FreeBSD__) || defined(__MACH__)
+    extern char** environ;
+#endif
 
 #ifdef EINTR