diff --git a/Makefrag b/Makefrag
index e50278e1..fcb14a9d 100644
--- a/Makefrag
+++ b/Makefrag
@@ -8,7 +8,7 @@ PROJECT := rocketchip
 CXX ?= g++
 CXXFLAGS := -O1
 
-SBT := java -Xmx2048M -Xss8M -XX:MaxPermSize=128M -jar sbt-launch.jar
+SBT := java -Xmx2048M -Xss8M -XX:MaxPermSize=256M -jar sbt-launch.jar
 SHELL := /bin/bash
 
 CHISEL_ARGS := $(PROJECT) $(MODEL) $(CONFIG) --W0W --minimumCompatibility 3.0.0 --backend $(BACKEND) --configName $(CONFIG) --compileInitializationUnoptimized --targetDir $(generated_dir)