diff --git a/library/asn1parse.c b/library/asn1parse.c
index 5b86aa6..f6b79ef 100644
--- a/library/asn1parse.c
+++ b/library/asn1parse.c
@@ -209,6 +209,24 @@
     return 0;
 }
 
+/*
+ * Get a bit string without unused bits
+ */
+int asn1_get_bitstring_null( unsigned char **p, const unsigned char *end,
+                             size_t *len )
+{
+    int ret;
+
+    if( ( ret = asn1_get_tag( p, end, len, ASN1_BIT_STRING ) ) != 0 )
+        return( ret );
+
+    if( --*len < 1 || *(*p)++ != 0 )
+        return( POLARSSL_ERR_ASN1_INVALID_DATA );
+
+    return( 0 );
+}
+
+
 
 /*
  *  Parses and splits an ASN.1 "SEQUENCE OF <tag>"