diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 21b8fc43275..0f0b4350f5b 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2000-02-13  Zack Weinberg  <zack@wolery.cumb.org>
+
+	* cpplib.c (do_define): Only free the old definition if it
+	actually had one.
+
 2000-02-13   Neil Booth  <NeilB@earthling.net>
 
 	* cppfiles.c (read_and_prescan): When emitting deferred
diff --git a/gcc/cpplib.c b/gcc/cpplib.c
index 9238d334602..844b89fda65 100644
--- a/gcc/cpplib.c
+++ b/gcc/cpplib.c
@@ -715,8 +715,9 @@ do_define (pfile, keyword)
       if (hp->type != T_POISON)
 	{
 	  /* Replace the old definition.  */
+	  if (hp->type == T_MACRO)
+	    free_definition (hp->value.defn);
 	  hp->type = T_MACRO;
-	  free_definition (hp->value.defn);
 	  hp->value.defn = mdef.defn;
 	}
     }