diff --git a/tasks.py b/tasks.py
index 3926691..6e06c99 100644
--- a/tasks.py
+++ b/tasks.py
@@ -192,7 +192,7 @@ def synth(c, target):
         pin_map_arg = f"--lpf {pin_map}"
     else:
         print(f"WARNING: no pin map at {pin_map}, executing place&route with no constraints")
-        pin_map_arg = f"--lpf-allow-unconstrained --lpf=lib/ulx3s_v20.lpf"
+        pin_map_arg = f"--lpf-allow-unconstrained --lpf=lib/ulx3s_v20.lpf --freq 100"
     nextpnr_out = out_nextpnr / module_name.with_suffix(".pnr")
     nextpnr_log = out_nextpnr / module_name.with_suffix(".log")
     nextpnr_timing = out_nextpnr / module_name.with_suffix(".timing.log")