diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 3de38fce277..1a9b26ae2cc 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -5,6 +5,8 @@ Thu Oct  8 17:00:18 1998  Richard Henderson  <rth@cygnus.com>
 
 Thu Oct  8 17:15:04 1998  Jeffrey A Law  (law@cygnus.com)
 
+	* i386/xm-cygwin32.h: Only define POSIX if it is not already defined.
+
 	* jump.c (jump_optimize): Revert accidental patch.
 
 	* Makefile.in (cpplib.o): Use unlibsubdir.
diff --git a/gcc/config/i386/xm-cygwin32.h b/gcc/config/i386/xm-cygwin32.h
index fd9c6db5923..67040fea7ce 100644
--- a/gcc/config/i386/xm-cygwin32.h
+++ b/gcc/config/i386/xm-cygwin32.h
@@ -52,4 +52,6 @@ do {									\
 #define PATH_SEPARATOR ';'
 
 /* This is needed so that protoize will compile.  */
+#ifndef POSIX
 #define POSIX
+#endif