diff --git a/tools/unit-tests/unit-keygen-xmss-params.c b/tools/unit-tests/unit-keygen-xmss-params.c
index b8e9a45f..0fe00fb0 100644
--- a/tools/unit-tests/unit-keygen-xmss-params.c
+++ b/tools/unit-tests/unit-keygen-xmss-params.c
@@ -22,8 +22,10 @@ static void mock_exit(int code);
 #define wc_XmssKey_ExportPubRaw mock_wc_XmssKey_ExportPubRaw
 #define wc_XmssKey_Free mock_wc_XmssKey_Free
 #define wc_ForceZero mock_wc_ForceZero
+#define wc_FreeRng mock_wc_FreeRng
 #include "../keytools/keygen.c"
 #undef wc_ForceZero
+#undef wc_FreeRng
 #undef wc_XmssKey_Free
 #undef wc_XmssKey_ExportPubRaw
 #undef wc_XmssKey_GetPrivLen
@@ -117,6 +119,12 @@ void mock_wc_ForceZero(void *mem, size_t len)
     (void)len;
 }
 
+int mock_wc_FreeRng(WC_RNG *rng)
+{
+    (void)rng;
+    return 0;
+}
+
 static void setup(void)
 {
     mock_xmss_param = NULL;