diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 4c92854baa6..60d81ad71ff 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+1999-02-09 10:30 -0500  Zack Weinberg  <zack@rabi.columbia.edu>
+
+	* cpplib.c (do_define): Allow redefining __STDC__ with -D.
+
 1999-02-09  Jim Blandy  <jimb@zwingli.cygnus.com>
 
 	* configure.in: For PowerPC configurations, accept "401", "ec603e",
diff --git a/gcc/cpplib.c b/gcc/cpplib.c
index 79046593964..32b70e6ed37 100644
--- a/gcc/cpplib.c
+++ b/gcc/cpplib.c
@@ -1410,7 +1410,7 @@ do_define (pfile, keyword)
       else if (hp->type == T_MACRO)
 	ok = ! compare_defs (pfile, mdef.defn, hp->value.defn);
       /* Redefining a constant is ok with -D.  */
-      else if (hp->type == T_CONST)
+      else if (hp->type == T_CONST || hp->type == T_STDC)
         ok = ! CPP_OPTIONS (pfile)->done_initializing;
       /* Print the warning if it's not ok.  */
       if (!ok)