diff --git a/library/asn1parse.c b/library/asn1parse.c
index b37523d..36aff6e 100644
--- a/library/asn1parse.c
+++ b/library/asn1parse.c
@@ -153,7 +153,7 @@
     if( ( ret = mbedtls_asn1_get_tag( p, end, &len, MBEDTLS_ASN1_INTEGER ) ) != 0 )
         return( ret );
 
-    if( len > sizeof( int ) || ( **p & 0x80 ) != 0 )
+    if( len == 0 || len > sizeof( int ) || ( **p & 0x80 ) != 0 )
         return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
 
     *val = 0;