diff --git a/nexus/pack.cc b/nexus/pack.cc
index cc86699a..bb62ec85 100644
--- a/nexus/pack.cc
+++ b/nexus/pack.cc
@@ -2000,7 +2000,7 @@ struct NexusPacker
                     copy_constraint(ci, id_CLKI, id_CLKO, 1);
                 } else if (ci->type == id_DCS) {
                     // For DCC copy the worst case ("fastest") constraint
-                    delay_t period_clk0, period_clk1;
+                    delay_t period_clk0 = 0, period_clk1 = 0;
                     bool have_clk0 = get_period(ci, id_CLK0, period_clk0);
                     bool have_clk1 = get_period(ci, id_CLK1, period_clk1);
                     if (have_clk0 && !have_clk1) {
@@ -2014,7 +2014,7 @@ struct NexusPacker
                     int div = int_or_default(ci->params, id_HF_CLK_DIV, 128);
                     const float tol = 1.07f; // OSCA has +/-7% frequency tolerance, assume the worst case.
                     set_period(ci, id_HFCLKOUT, delay_t((1.0e6 / 450) * (div + 1) / tol));
-                    set_period(ci, id_LFCLKOUT, delay_t((1.0e3 / 10) / tol));
+                    set_period(ci, id_LFCLKOUT, delay_t((1.0e9 /  32) / tol));
                 } else if (ci->type == id_PLL_CORE) {
                     static const std::array<IdString, 6> div{id_DIVA, id_DIVB, id_DIVC, id_DIVD, id_DIVE, id_DIVF};
                     static const std::array<IdString, 6> output{id_CLKOP,  id_CLKOS,  id_CLKOS2,