1 files changed, 1 insertions, 1 deletions
diff --git a/generic/tclIO.c b/generic/tclIO.c
index 7303314..884bd83 100644
--- a/generic/tclIO.c
+++ b/generic/tclIO.c
@@ -7667,7 +7667,7 @@ Tcl_BadChannelOption(
 	}
 	Tcl_ResetResult(interp);
 	errObj = Tcl_ObjPrintf("bad option \"%s\": should be one of ",
-                optionName);
+                optionName ? optionName : "");
 	argc--;
 	for (i = 0; i < argc; i++) {
 	    Tcl_AppendPrintfToObj(errObj, "-%s, ", argv[i]);