diff --git a/configure.ac b/configure.ac
index 7b20e11c..20d41a70 100644
--- a/configure.ac
+++ b/configure.ac
@@ -491,6 +491,10 @@ case $host_os in
 		;;
 esac
 
+# As a GNU extension, glibc declares environ in unistd.h, which is one of
+# the AC_INCLUDES_DEFAULT.
+AC_CHECK_DECLS([environ])
+
 dnl **********************************
 dnl *** va_copy checks (from GLib) ***
 dnl **********************************
diff --git a/dbus/dbus-spawn.c b/dbus/dbus-spawn.c
index df6eafd9..0be8800c 100644
--- a/dbus/dbus-spawn.c
+++ b/dbus/dbus-spawn.c
@@ -45,7 +45,12 @@
 #include <systemd/sd-journal.h>
 #endif
 
+#if defined(__APPLE__)
+# include <crt_externs.h>
+# define environ (*_NSGetEnviron ())
+#elif !HAVE_DECL_ENVIRON
 extern char **environ;
+#endif
 
 /**
  * @addtogroup DBusInternalsUtils
diff --git a/dbus/dbus-sysdeps-util.c b/dbus/dbus-sysdeps-util.c
index f35c9666..44cc6a23 100644
--- a/dbus/dbus-sysdeps-util.c
+++ b/dbus/dbus-sysdeps-util.c
@@ -35,6 +35,8 @@
 #elif (defined __APPLE__)
 # include <crt_externs.h>
 # define environ (*_NSGetEnviron())
+#elif HAVE_DECL_ENVIRON && defined(HAVE_UNISTD_H)
+# include <unistd.h>
 #else
 extern char **environ;
 #endif
diff --git a/dbus/dbus-sysdeps.c b/dbus/dbus-sysdeps.c
index c58377bd..d1a96d12 100644
--- a/dbus/dbus-sysdeps.c
+++ b/dbus/dbus-sysdeps.c
@@ -52,6 +52,8 @@
 #elif (defined __APPLE__)
 # include <crt_externs.h>
 # define environ (*_NSGetEnviron())
+#elif HAVE_DECL_ENVIRON && defined(HAVE_UNISTD_H)
+# include <unistd.h>
 #else
 extern char **environ;
 #endif
diff --git a/tools/dbus-update-activation-environment.c b/tools/dbus-update-activation-environment.c
index 160ac5d0..452e5053 100644
--- a/tools/dbus-update-activation-environment.c
+++ b/tools/dbus-update-activation-environment.c
@@ -62,9 +62,12 @@
 #ifdef DBUS_WIN
 /* The Windows C runtime uses a different name */
 #define environ _environ
+#elif defined(__APPLE__)
+# include <crt_externs.h>
+# define environ (*_NSGetEnviron ())
+#elif HAVE_DECL_ENVIRON && defined(HAVE_UNISTD_H)
+# include <unistd.h>
 #else
-/* apparently this is the portable way to get the entire environment...
- * GNU platforms also put it in unistd.h but that's not portable */
 extern char **environ;
 #endif