diff --git a/assume_role.sh b/assume_role.sh
index 4aa39cb..fa7286e 100644
--- a/assume_role.sh
+++ b/assume_role.sh
@@ -6,7 +6,7 @@ function assume {
   token=$3
   duration=900
   if echo "$4" | grep "^[0-9]\{3,4\}$" > /dev/null; then duration=$4; fi
-  mfa_device="$(aws --profile $profile --region $region iam list-mfa-devices --query MFADevices[0].SerialNumber --output text  )"
+  mfa_device="$(aws --profile $profile --region $region iam list-mfa-devices --query "MFADevices[0].SerialNumber" --output text  )"
   result="$(aws --profile $profile --region $region \
     sts assume-role --role-arn "$role" \
     --serial-number "$mfa_device" --role-session-name "`whoami`" --duration-seconds "$duration" \