diff --git a/openlane/Makefile b/openlane/Makefile
index aea51b8..4d42a79 100644
--- a/openlane/Makefile
+++ b/openlane/Makefile
@@ -18,8 +18,8 @@
 CONFIG = $(foreach block,$(BLOCKS), ./$(block)/config.tcl)
 CLEAN = $(foreach block,$(BLOCKS), clean-$(block))
 
-OPENLANE_TAG ?= mpw6
-OPENLANE_IMAGE_NAME ?= riscduino/openlane:$(OPENLANE_TAG)
+OPENLANE_TAG = mpw6
+OPENLANE_IMAGE_NAME = riscduino/openlane:$(OPENLANE_TAG)
 OPENLANE_BASIC_COMMAND = "cd $(PWD)/../openlane && flow.tcl -design ./$* -save_path .. -save -tag $* -overwrite"
 OPENLANE_INTERACTIVE_COMMAND = "cd $(PWD)/../openlane && flow.tcl -design ./$* -save_path .. -save -tag $* -overwrite -it -file ./$*/interactive.tcl"