diff --git a/rules/pulpos/default_rules.mk b/rules/pulpos/default_rules.mk
index 400b82e..ef7822f 100644
--- a/rules/pulpos/default_rules.mk
+++ b/rules/pulpos/default_rules.mk
@@ -9,7 +9,7 @@ endif
 
 platform ?= rtl
 
-export ETH_QUESTA_PREFIX ?= ""
+export ETH_QUESTA_PREFIX ?=
 
 ifdef PULP_RUNTIME_GCC_TOOLCHAIN
 PULP_CC := $(PULP_RUNTIME_GCC_TOOLCHAIN)/bin/$(PULP_CC)