diff --git a/epan/dtd_parse.l b/epan/dtd_parse.l
index bec26323f6..551823ddda 100644
--- a/epan/dtd_parse.l
+++ b/epan/dtd_parse.l
@@ -63,8 +63,8 @@
 
 	static void* pParser;
 	static GString* input_string;
-	static guint offsetx;
-	static guint len;
+	static size_t offsetx;
+	static size_t len;
 	static gchar* location;
 	static gchar* attr_name;
 
@@ -328,7 +328,7 @@ extern dtd_build_data_t* dtd_parse(GString* s) {
 
 	input_string = s;
 	offsetx = 0;
-	len = (guint) input_string->len;
+	len = input_string->len;
 
 	pParser = DtdParseAlloc(g_malloc);