diff --git a/opendmarc/opendmarc-arcseal.c b/opendmarc/opendmarc-arcseal.c
index 73eebb7..9264eee 100644
--- a/opendmarc/opendmarc-arcseal.c
+++ b/opendmarc/opendmarc-arcseal.c
@@ -29,7 +29,7 @@
 #include "opendmarc.h"
 
 #define OPENDMARC_ARCSEAL_MAX_FIELD_NAME_LEN 255
-#define OPENDMARC_ARCSEAL_MAX_TOKEN_LEN      512
+#define OPENDMARC_ARCSEAL_MAX_TOKEN_LEN      768
 
 /* tables */
 struct opendmarc_arcseal_lookup
@@ -167,7 +167,12 @@ opendmarc_arcseal_parse(u_char *hdr, struct arcseal *as)
 		if (*token_ptr == '\0')
 			return 0;
 		tag_label = strsep(&token_ptr, "=");
+		if (tag_label == NULL)
+			return 0;
+
 		tag_value = opendmarc_arcseal_strip_whitespace(token_ptr);
+		if (tag_value == NULL)
+			return 0;
 
 		tag_code = opendmarc_arcseal_convert(as_tags, tag_label);
 
diff --git a/opendmarc/opendmarc-arcseal.h b/opendmarc/opendmarc-arcseal.h
index 4eb0927..6e11a06 100644
--- a/opendmarc/opendmarc-arcseal.h
+++ b/opendmarc/opendmarc-arcseal.h
@@ -32,7 +32,7 @@
 /* max header tag value length (short) */
 #define OPENDMARC_ARCSEAL_MAX_SHORT_VALUE_LEN 256
 /* max header tag value length (long) */
-#define OPENDMARC_ARCSEAL_MAX_LONG_VALUE_LEN  512
+#define OPENDMARC_ARCSEAL_MAX_LONG_VALUE_LEN  768
 
 /* names and field labels */
 #define OPENDMARC_ARCSEAL_HDRNAME	"ARC-Seal"