diff --git a/src/simple_exim_test.sh b/src/simple_exim_test.sh
index a84d8f1..c65a4c3 100755
--- a/src/simple_exim_test.sh
+++ b/src/simple_exim_test.sh
@@ -2,8 +2,11 @@
 
 set -e
 
-LIB=`pwd`/libexim-encrypt-dlfunc.so
-CLEARTEXT="X-Originating-IP: [dead:beef:dead:beef:dead:beef:dead:beef]"
+# copy to /tmp to keep call to exim under 256 chars (prevent problems on Ubuntu)
+install -t /tmp libexim-encrypt-dlfunc.so
+
+LIB=/tmp/libexim-encrypt-dlfunc.so
+CLEARTEXT="127.88.99.23" # keep short; see above
 PASSWORD="`openssl rand -base64 32`"
 
 CIPHERTEXT=$(exim -be "\${dlfunc{${LIB}}{sodium_crypto_secretbox_encrypt_password}{${PASSWORD}}{${CLEARTEXT}}}")