diff --git a/.travis.yml b/.travis.yml
index e25cf813..47c64a35 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -12,11 +12,11 @@ python:
 env:
 - MODE=mitogen MITOGEN_TEST_DISTRO=debian
 - MODE=mitogen MITOGEN_TEST_DISTRO=centos
-- MODE=debops_common
+- MODE=debops_common ANSIBLE_VERSION=2.4.3.0
+- MODE=debops_common ANSIBLE_VERSION=2.5.1
 - MODE=ansible ANSIBLE_VERSION=2.4.3.0 MITOGEN_TEST_DISTRO=debian
-- MODE=ansible ANSIBLE_VERSION=2.4.3.0 MITOGEN_TEST_DISTRO=centos
-- MODE=ansible ANSIBLE_VERSION=2.5.0 MITOGEN_TEST_DISTRO=centos
-- MODE=ansible ANSIBLE_VERSION=2.5.0 MITOGEN_TEST_DISTRO=debian
+- MODE=ansible ANSIBLE_VERSION=2.5.1 MITOGEN_TEST_DISTRO=centos
+- MODE=ansible ANSIBLE_VERSION=2.5.1 MITOGEN_TEST_DISTRO=debian
 
 install:
 - pip install -r dev_requirements.txt
diff --git a/.travis/debops_common_tests.sh b/.travis/debops_common_tests.sh
index b75484c2..f0537a85 100755
--- a/.travis/debops_common_tests.sh
+++ b/.travis/debops_common_tests.sh
@@ -4,6 +4,7 @@
 TMPDIR="/tmp/debops-$$"
 TRAVIS_BUILD_DIR="${TRAVIS_BUILD_DIR:-`pwd`}"
 TARGET_COUNT="${TARGET_COUNT:-2}"
+ANSIBLE_VERSION="${ANSIBLE_VERSION:-2.4.3.0}"
 MITOGEN_TEST_DISTRO=debian  # Naturally DebOps only supports Debian.
 
 export PYTHONPATH="${PYTHONPATH}:${TRAVIS_BUILD_DIR}"
@@ -26,7 +27,7 @@ mkdir "$TMPDIR"
 
 
 echo travis_fold:start:job_setup
-pip install -qqqU debops==0.7.2 ansible==2.4.3.0
+pip install -qqqU debops==0.7.2 ansible==${ANSIBLE_VERSION}
 debops-init "$TMPDIR/project"
 cd "$TMPDIR/project"
 
diff --git a/ansible_mitogen/services.py b/ansible_mitogen/services.py
index 843f3013..fee50934 100644
--- a/ansible_mitogen/services.py
+++ b/ansible_mitogen/services.py
@@ -448,7 +448,7 @@ class FileService(mitogen.service.Service):
         Defer a function call to the Broker thread in order to accurately
         measure the bytes pending in `stream`'s queue.
 
-        This must be done synchronized with the Broker, as scheduler
+        This must be done synchronized with the Broker, as OS scheduler
         uncertainty could cause Sender.send()'s deferred enqueues to be
         processed very late, making the output queue look much emptier than it
         really is (or is about to become).