diff --git a/library/dhm.c b/library/dhm.c
index 07d722e..bddd076 100644
--- a/library/dhm.c
+++ b/library/dhm.c
@@ -127,7 +127,8 @@
  */
 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 )
 {
     int ret, n;
     size_t n1, n2, n3;
@@ -203,7 +204,8 @@
  */
 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 )
 {
     int ret, n;