diff --git a/emu.sh b/emu.sh
index 82485e738..9c9f2b11c 100755
--- a/emu.sh
+++ b/emu.sh
@@ -3,7 +3,7 @@
 source emu.config 2>/dev/null
 
 EXE=build/unix/micropython
-OPTLEVEL="${OPTLEVEL:-0}"
+OPTLEVEL="${OPTLEVEL:-1}"
 MAIN="${MAIN:-main.py}"
 BROWSER="${BROWSER:-chromium}"
 if file $EXE | grep -q 80386 ; then
diff --git a/tests/run_tests.sh b/tests/run_tests.sh
index 66625bbb8..dd27845fe 100755
--- a/tests/run_tests.sh
+++ b/tests/run_tests.sh
@@ -1,6 +1,7 @@
 #!/bin/bash
 
 MICROPYTHON=../build/unix/micropython
+PYOPT=1
 
 results=()
 error=0
@@ -13,7 +14,7 @@ fi
 
 for i in $list; do
     echo
-    if $MICROPYTHON $i; then
+    if $MICROPYTHON -O$PYOPT $i; then
         results+=("OK   $i")
     else
         results+=("FAIL $i")
diff --git a/tests/run_tests_device_emu.sh b/tests/run_tests_device_emu.sh
index 9e2356101..ab8eeb0cd 100755
--- a/tests/run_tests_device_emu.sh
+++ b/tests/run_tests_device_emu.sh
@@ -1,8 +1,11 @@
 #!/bin/bash
 
+MICROPYTHON=../build/unix/micropython
+PYOPT=0
+
 # run emulator
 cd ../src
-../build/unix/micropython -O0 main.py >/dev/null &
+$MICROPYTHON -O$PYOPT main.py >/dev/null &
 upy_pid=$!
 sleep 1