diff --git a/Makefile b/Makefile
index c5c5150..4161620 100644
--- a/Makefile
+++ b/Makefile
@@ -24,7 +24,7 @@ $(TOP_BIN): $(TOP_ASC)
 # Place and rouite
 $(TOP_ASC): $(TOP_JSON) $(PCF)
 	nextpnr-ice40 -q -l $(BUILD_DIR)/nextpnr.log --$(FAMILY) --package $(PACKAGE) \
-		--freq $(FREQ) --top $(TOP) --pcf $(PCF) --asc $(TOP_ASC) --json $(TOP_JSON) \
+		--top $(TOP) --pcf $(PCF) --asc $(TOP_ASC) --json $(TOP_JSON) \
 		$(DOSVG)
 
 # Synthesys
diff --git a/icesugar.pcf b/icesugar.pcf
index e7e8ac7..f39ea59 100644
--- a/icesugar.pcf
+++ b/icesugar.pcf
@@ -54,8 +54,11 @@ set_io -nowarn P4_2     20
 set_io -nowarn P4_3     19
 set_io -nowarn P4_4     18
 
-#spi
+# spi
 set_io -nowarn SPI_SS   16
 set_io -nowarn SPI_SCK  15
 set_io -nowarn SPI_MOSI 17
 set_io -nowarn SPI_MISO 14
+
+# Clock constraint
+set_frequency clock 30