Update Makefile
diff --git a/Makefile b/Makefile
index e246405..150e485 100644
--- a/Makefile
+++ b/Makefile
@@ -21,7 +21,7 @@
 SIM?=RTL
 
 export SKYWATER_COMMIT=c094b6e83a4f9298e47f696ec5a7fd53535ec5eb
-export OPEN_PDKS_COMMIT=7519dfb04400f224f140749cda44ee7de6f5e095
+export OPEN_PDKS_COMMIT?=7519dfb04400f224f140749cda44ee7de6f5e095
 export PDK_MAGIC_COMMIT=7d601628e4e05fd17fcb80c3552dacb64e9f6e7b
 export OPENLANE_TAG=2022.02.23_02.50.41