diff --git a/speck.h b/speck.h
index f0402f2..d92d455 100644
--- a/speck.h
+++ b/speck.h
@@ -19,4 +19,4 @@ int speck_ctr (unsigned char *out, const unsigned char *in,
                const unsigned char *n,
                speck_context_t ctx);
 
-int speck_expand_key (const unsigned char *k, speck_context_t ctx);
+int speck_expand_key (const unsigned char *k, speck_context_t *ctx);
diff --git a/transform_speck.c b/transform_speck.c
index cde6394..d411a41 100644
--- a/transform_speck.c
+++ b/transform_speck.c
@@ -173,7 +173,7 @@ static int setup_speck_key(transop_speck_t *priv, const uint8_t *key, ssize_t ke
   // FOR NOW: USE KEY ITSELF
   memcpy (key_mat_buf, key, ((key_size>32)?32:key_size) );
 
-  speck_expand_key (key_mat_buf, priv->ctx);
+  speck_expand_key (key_mat_buf, &(priv->ctx));
   traceEvent(TRACE_DEBUG, "Speck key setup completed\n");
 
   return(0);