diff --git a/flow/designs/asap7/mock-array/Element/config.mk b/flow/designs/asap7/mock-array/Element/config.mk
index 7965743b6a..4f4f4c3830 100644
--- a/flow/designs/asap7/mock-array/Element/config.mk
+++ b/flow/designs/asap7/mock-array/Element/config.mk
@@ -27,7 +27,7 @@ export IO_CONSTRAINTS         = designs/asap7/mock-array/Element/io.tcl
 export PDN_TCL                = $(FLOW_HOME)/platforms/asap7/openRoad/pdn/BLOCK_grid_strategy.tcl
 
 # Detailed routing should be easy, limit iterations
-export DETAILED_ROUTE_END_ITERATION = 6
+export DETAILED_ROUTE_END_ITERATION ?= 6
 
 export MIN_ROUTING_LAYER = M2
 # M5 is the top PDN layer, so don't exceed that.
diff --git a/flow/designs/asap7/mock-array/config.mk b/flow/designs/asap7/mock-array/config.mk
index 0910d00083..52aa1de51e 100644
--- a/flow/designs/asap7/mock-array/config.mk
+++ b/flow/designs/asap7/mock-array/config.mk
@@ -57,7 +57,7 @@ power:
 	$(OPENSTA_EXE) -no_init -exit designs/asap7/mock-array/power.tcl
 
 # Routing by abutment should be easy, limit iterations
-export DETAILED_ROUTE_END_ITERATION = 6
+export DETAILED_ROUTE_END_ITERATION ?= 6
 
 export MAX_ROUTING_LAYER = M9
 export ROUTING_LAYER_ADJUSTMENT = 0.45