diff --git a/library/dhm.c b/library/dhm.c
index 8bc9f0e..406404a 100644
--- a/library/dhm.c
+++ b/library/dhm.c
@@ -460,6 +460,8 @@
 
     ret = 0;
 
+    dhm->len = mpi_size( &dhm->P );
+
 exit:
 #if defined(POLARSSL_PEM_PARSE_C)
     pem_free( &pem );