diff --git a/rules/pulpos/targets/pulp_cluster.mk b/rules/pulpos/targets/pulp_cluster.mk
index 7e9b217..033b2c6 100644
--- a/rules/pulpos/targets/pulp_cluster.mk
+++ b/rules/pulpos/targets/pulp_cluster.mk
@@ -67,9 +67,11 @@ ifndef gui
 vsim-flags = -c
 endif
 
+VSIM ?= vsim
+
 run:
 ifdef gui
-	vsim $(vsim-flags) -do "set  VSIM_PATH $(VSIM_PATH); set  APP $(TARGET_BUILD_DIR)/$(PULP_APP)/$(PULP_APP); source $(VSIM_PATH)/scripts/start.tcl"
+	$(VSIM) $(vsim-flags) -do "set  VSIM_PATH $(VSIM_PATH); set  APP $(TARGET_BUILD_DIR)/$(PULP_APP)/$(PULP_APP); source $(VSIM_PATH)/scripts/start.tcl"
 else
-	vsim $(vsim-flags) -do "set  VSIM_PATH $(VSIM_PATH); set  APP $(TARGET_BUILD_DIR)/$(PULP_APP)/$(PULP_APP); source $(VSIM_PATH)/scripts/run_and_exit.tcl"
+	$(VSIM) $(vsim-flags) -do "set  VSIM_PATH $(VSIM_PATH); set  APP $(TARGET_BUILD_DIR)/$(PULP_APP)/$(PULP_APP); source $(VSIM_PATH)/scripts/run_and_exit.tcl"
 endif