diff --git a/utils/swift_build_support/swift_build_support/products/cmake_product.py b/utils/swift_build_support/swift_build_support/products/cmake_product.py
index 6e4e633078636..39ac9dd026e52 100644
--- a/utils/swift_build_support/swift_build_support/products/cmake_product.py
+++ b/utils/swift_build_support/swift_build_support/products/cmake_product.py
@@ -85,7 +85,7 @@ def build_with_cmake(self, build_targets, build_type, build_args,
                        + build_args + build_targets)
 
     def test_with_cmake(self, executable_target, results_targets,
-                        build_type, build_args):
+                        build_type, build_args, test_env=None):
         assert self.toolchain.cmake is not None
         cmake_build = []
 
@@ -117,7 +117,9 @@ def target_flag(target):
                 if test_target.startswith("check-swift") and self.args.test_paths:
                     test_target = test_target + "-custom"
 
-                shell.call(cmake_build + target_flag(test_target))
+                # note that passing variables via test_env won't affect lit tests -
+                # lit.cfg will filter environment variables out!
+                shell.call(cmake_build + target_flag(test_target), env=test_env)
 
                 print("--- %s finished ---" % target)
 
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..97198ca064523 100644
--- a/utils/swift_build_support/swift_build_support/products/cmark.py
+++ b/utils/swift_build_support/swift_build_support/products/cmark.py
@@ -94,8 +94,14 @@ def test(self, host_target):
             # Xcode generator uses "RUN_TESTS" instead of "test".
             results_targets = ['RUN_TESTS']
 
+        test_env = {
+            "CTEST_OUTPUT_ON_FAILURE": "ON"
+        }
+
+        # see the comment in cmake_product.py if you want to copy this code to pass
+        # environment variables to tests
         self.test_with_cmake(executable_target, results_targets,
-                             self.args.cmark_build_variant, [])
+                             self.args.cmark_build_variant, [], test_env)
 
     def should_install(self, host_target):
         """should_install() -> Bool