diff --git a/library/asn1parse.c b/library/asn1parse.c
index e4f46eb..8c167df 100644
--- a/library/asn1parse.c
+++ b/library/asn1parse.c
@@ -154,7 +154,7 @@
     if( ( ret = asn1_get_tag( p, end, &len, ASN1_INTEGER ) ) != 0 )
         return( ret );
 
-    if( len > sizeof( int ) || ( **p & 0x80 ) != 0 )
+    if( len == 0 || len > sizeof( int ) || ( **p & 0x80 ) != 0 )
         return( POLARSSL_ERR_ASN1_INVALID_LENGTH );
 
     *val = 0;