diff --git a/include/polarssl/dhm.h b/include/polarssl/dhm.h
index 703224275..f63eefd12 100644
--- a/include/polarssl/dhm.h
+++ b/include/polarssl/dhm.h
@@ -76,7 +76,7 @@ int dhm_read_params( dhm_context *ctx,
  *
  * \return         0 if successful, or an POLARSSL_ERR_DHM_XXX error code
  */
-int dhm_make_params( dhm_context *ctx, int s_size,
+int dhm_make_params( dhm_context *ctx, int x_size,
                      unsigned char *output, int *olen,
                      int (*f_rng)(void *), void *p_rng );