diff --git a/src/acconfig.h b/src/acconfig.h
index 41a19a38440c25bd0896a2f59dc3ad899570b3d3..a1de6a690a1437629e06334d7ad1e1afc835bb36 100644
--- a/src/acconfig.h
+++ b/src/acconfig.h
@@ -112,6 +112,9 @@
 /* define if declaration of getenv is missing */
 #undef GETENV_DECL_MISSING
 
+/* Define if we can declare 'extern char **environ' */
+#undef DECLARE_ENVIRON
+
 /* What byteorder does your machie use most machines use 4321, PC use 1234 */
 #define BYTEORDER 0