diff --git a/README.md b/README.md
index b7d5c837fe46f..7283b327c0cae 100644
--- a/README.md
+++ b/README.md
@@ -132,6 +132,7 @@ compiler crashes.
 
 2. Specify the local toolchain for Xcode's use via `Xcode->Toolchains`.
 
+
 ### Build Failures
 
 Try the suggestions in
diff --git a/utils/swift_build_support/swift_build_support/products/cmark.py b/utils/swift_build_support/swift_build_support/products/cmark.py
index bde199b37e0de..1408a7462a986 100644
--- a/utils/swift_build_support/swift_build_support/products/cmark.py
+++ b/utils/swift_build_support/swift_build_support/products/cmark.py
@@ -12,6 +12,7 @@
 
 from . import cmake_product
 from . import earlyswiftdriver
+from .. import shell
 
 
 class CMark(cmake_product.CMakeProduct):
@@ -94,8 +95,13 @@ def test(self, host_target):
             # Xcode generator uses "RUN_TESTS" instead of "test".
             results_targets = ['RUN_TESTS']
 
-        self.test_with_cmake(executable_target, results_targets,
-                             self.args.cmark_build_variant, [])
+        test_env = {
+            "CTEST_OUTPUT_ON_FAILURE": "ON"
+        }
+
+        with shell.pushenv(test_env):
+            self.test_with_cmake(executable_target, results_targets,
+                                 self.args.cmark_build_variant, [])
 
     def should_install(self, host_target):
         """should_install() -> Bool
diff --git a/utils/swift_build_support/swift_build_support/shell.py b/utils/swift_build_support/swift_build_support/shell.py
index 222d540dd2c95..1198b8b230026 100644
--- a/utils/swift_build_support/swift_build_support/shell.py
+++ b/utils/swift_build_support/swift_build_support/shell.py
@@ -162,6 +162,29 @@ def pushd(path, dry_run=None, echo=True):
     if not dry_run:
         os.chdir(old_dir)
 
+@contextmanager
+def pushenv(env, dry_run=None, echo=True):
+    saved_env = {}
+    for name in env.keys():
+        if dry_run or echo:
+            _echo_command(dry_run, ['export', name + '=' + env[name]])
+        if not dry_run:
+            if name in os.environ:
+                saved_env[name] = os.environ[name]
+            os.environ[name] = env[name]
+    yield
+    for name in env.keys():
+        if name in saved_env:
+            if dry_run or echo:
+                _echo_command(dry_run, ['export', name + '=' + saved_env[name]])
+            if not dry_run:
+                os.environ[name] = saved_env[name]
+        else:
+            if dry_run or echo:
+                _echo_command(dry_run, ['unset', name])
+            if not dry_run:
+                del os.environ[name]
+
 
 def makedirs(path, dry_run=None, echo=True):
     dry_run = _coerce_dry_run(dry_run)