diff --git a/hw/core/clock.c b/hw/core/clock.c
index a19c7db..e212865 100644
--- a/hw/core/clock.c
+++ b/hw/core/clock.c
@@ -108,7 +108,6 @@
 
 void clock_propagate(Clock *clk)
 {
-    assert(clk->source == NULL);
     trace_clock_propagate(CLOCK_PATH(clk));
     clock_propagate_period(clk, true);
 }