diff --git a/include/polarssl/dhm.h b/include/polarssl/dhm.h
index 1cbfc6c..52b0bf9 100644
--- a/include/polarssl/dhm.h
+++ b/include/polarssl/dhm.h
@@ -90,7 +90,8 @@
  */
 int dhm_make_params( dhm_context *ctx, int x_size,
                      unsigned char *output, size_t *olen,
-                     int (*f_rng)(void *), void *p_rng );
+                     int (*f_rng)(void *, unsigned char *, size_t),
+                     void *p_rng );
 
 /**
  * \brief          Import the peer's public value G^Y
@@ -118,7 +119,8 @@
  */
 int dhm_make_public( dhm_context *ctx, int x_size,
                      unsigned char *output, size_t olen,
-                     int (*f_rng)(void *), void *p_rng );
+                     int (*f_rng)(void *, unsigned char *, size_t),
+                     void *p_rng );
 
 /**
  * \brief          Derive and export the shared secret (G^Y)^X mod P