Fix failure in Travis CI

Signed-off-by: Yanray Wang <yanray.wang@arm.com>
diff --git a/.travis.yml b/.travis.yml
index eaf817a..54df776 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -53,7 +53,7 @@
         - tests/scripts/test_psa_constant_names.py
         - tests/ssl-opt.sh
         # Modern OpenSSL does not support fixed ECDH or null ciphers.
-        - tests/compat.sh -p OpenSSL -e 'NULL\|ECDH-'
+        - tests/compat.sh -p OpenSSL -e 'NULL\|ECDH_'
         - tests/scripts/travis-log-failure.sh
         # GnuTLS supports CAMELLIA but compat.sh doesn't properly enable it.
         - tests/compat.sh -p GnuTLS -e 'CAMELLIA'