diff --git a/build.sh b/build.sh
index dbd5d21..28f2ff9 100755
--- a/build.sh
+++ b/build.sh
@@ -189,7 +189,7 @@ if [[ ${FAST} != "fast" ]]; then
 
     if [[ "${NACL_GLIBC}" != "1" ]]; then
       # Do things specific to newlib.
-      export CXXFLAGS="${CXXFLAGS} -I${INCLUDE_OVERRIDE} -DHAVE_FORKPTY -DHAVE_SYS_UIO_H"
+      export CXXFLAGS="${CXXFLAGS} -I${INCLUDE_OVERRIDE} -DHAVE_FORKPTY -DHAVE_SYS_UIO_H -O2"
     fi
     # Do configure step in a subshell as we need to fake it out a little.
     (
diff --git a/src/Makefile b/src/Makefile
index c9fbeed..202bcd2 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -81,7 +81,7 @@ OBJCOPY:=$(TC_PATH)/../$(OSNAME)_x86_newlib/bin/i686-nacl-objcopy
 # Project Build flags
 # TODO: Remove --pnacl-exceptions once exceptions are fully supported by PNaCl.
 override CXXFLAGS+=-pthread $(WARNINGS) -I$(NACL_SDK_ROOT)/include -fno-builtin \
-	--pnacl-exceptions=sjlj
+	--pnacl-exceptions=sjlj -O2
 
 COMPAT_INC:=-I${TC_PATH}/ARCH-nacl/usr/include/glibc-compat
 NEWLIB_CXXFLAGS:=$(CXXFLAGS) -DUSE_NEWLIB $(COMPAT_INC)