diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 6e4a1223e3..7245a39379 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,8 @@
 Fri Nov 11 10:51:07 1994  Jeff Law  (law@snake.cs.utah.edu)
 
+	* ch-exp.y (yylex): Fix off-by-one error when converting string to
+	lowercase.  Null terminate new string.
+
 	* hppa-tdep.c (rp_saved): Handle IMPORT stubs too.
 
 	* somsolib.c (som_solib_add): Check the value of __dld_flags, if
diff --git a/gdb/ch-exp.y b/gdb/ch-exp.y
index b7a0b5ec8c..191abe6003 100644
--- a/gdb/ch-exp.y
+++ b/gdb/ch-exp.y
@@ -1844,11 +1844,12 @@ yylex ()
 
     if (inputname != NULL)
       {
-	char *simplename = (char*) alloca (strlen (inputname));
+	char *simplename = (char*) alloca (strlen (inputname) + 1);
 
 	char *dptr = simplename, *sptr = inputname;
 	for (; *sptr; sptr++)
 	  *dptr++ = isupper (*sptr) ? tolower(*sptr) : *sptr;
+	*dptr = '\0';
 
 	/* See if it is a reserved identifier. */
 	for (i = 0; i < sizeof (idtokentab) / sizeof (idtokentab[0]); i++)