diff --git a/pdf.c b/pdf.c
index a0af87fb5907579763669623b5c078343bcc5c06..1188dbfb7f6dd271cb867ddbbd6018d37a9c896e 100644
--- a/pdf.c
+++ b/pdf.c
@@ -116,7 +116,7 @@ pdf_parser(void)
 	H_RULE(line,	h_many(h_not_in("\r\n", 2)));
 
 	/* character classes */
-#define WCHARS "\t\n\f\r "
+#define WCHARS "\0\t\n\f\r "
 #define DCHARS "()<>[]{}/%"
 	H_RULE(wchar,	IN(WCHARS));			/* white-space */
 	//XXX H_RULE(dchar,	IN(DCHARS));			/* delimiter */