diff --git a/lib/asn1_decoder.c b/lib/asn1_decoder.c
index fef5d2e..1ef0cec 100644
--- a/lib/asn1_decoder.c
+++ b/lib/asn1_decoder.c
@@ -228,7 +228,7 @@
 		hdr = 2;
 
 		/* Extract a tag from the data */
-		if (unlikely(dp >= datalen - 1))
+		if (unlikely(datalen - dp < 2))
 			goto data_overrun_error;
 		tag = data[dp++];
 		if (unlikely((tag & 0x1f) == ASN1_LONG_TAG))
@@ -274,7 +274,7 @@
 				int n = len - 0x80;
 				if (unlikely(n > 2))
 					goto length_too_long;
-				if (unlikely(dp >= datalen - n))
+				if (unlikely(n > datalen - dp))
 					goto data_overrun_error;
 				hdr += n;
 				for (len = 0; n > 0; n--) {