diff --git a/build_opts/ARM_MESI_Three_Level b/build_opts/ARM_MESI_Three_Level
index 1836fb095b..29a429ce68 100644
--- a/build_opts/ARM_MESI_Three_Level
+++ b/build_opts/ARM_MESI_Three_Level
@@ -2,5 +2,5 @@
 # All rights reserved.
 
 TARGET_ISA = 'arm'
-CPU_MODELS = 'TimingSimpleCPU, O3CPU'
+CPU_MODELS = 'TimingSimpleCPU,O3CPU'
 PROTOCOL = 'MESI_Three_Level'