diff --git a/techlibs/common/synth.cc b/techlibs/common/synth.cc
index e7a192c07..513702357 100644
--- a/techlibs/common/synth.cc
+++ b/techlibs/common/synth.cc
@@ -225,9 +225,9 @@ struct SynthPass : public ScriptPass
 			run("peepopt");
 			run("opt_clean");
 			if (help_mode)
-				run("techmap -map +/cmp2lut.v", " (if -lut)");
+				run("techmap -map +/cmp2lut.v -map +/cmp2lcu.v", " (if -lut)");
 			else
-				run(stringf("techmap -map +/cmp2lut.v -D LUT_WIDTH=%d", lut));
+				run(stringf("techmap -map +/cmp2lut.v -map +/cmp2lcu.v -D LUT_WIDTH=%d", lut));
 			if (!noalumacc)
 				run("alumacc", "  (unless -noalumacc)");
 			if (!noshare)