diff --git a/library/pk_wrap.c b/library/pk_wrap.c
index c45fbd4..d61a7cb 100644
--- a/library/pk_wrap.c
+++ b/library/pk_wrap.c
@@ -729,7 +729,7 @@
     }
 
 done:
-    ret = mbedtls_ecdsa_raw_to_der(key_bits, sig, sig_size, sig, sig_size, sig_len);
+    ret = mbedtls_ecdsa_raw_to_der(key_bits, sig, *sig_len, sig, sig_size, sig_len);
 
     return ret;
 }