diff --git a/run.dylan b/run.dylan
index 33b264a..6c7a11a 100644
--- a/run.dylan
+++ b/run.dylan
@@ -31,6 +31,7 @@ define function test-temp-directory () => (d :: false-or(<directory-locator>))
                         full-component-name(*component*));
     let test-directory
       = subdirectory-locator(base, "_test", uniquifier, safe-name);
+    test-output("test-directory = %s\n", test-directory);
     fs/ensure-directories-exist(test-directory);
     test-directory
   end
diff --git a/tests/library.dylan b/tests/library.dylan
index 10c1da9..3790b92 100644
--- a/tests/library.dylan
+++ b/tests/library.dylan
@@ -15,7 +15,7 @@ define library testworks-test-suite
     import: { format, streams };
   use strings;
   use system,
-    import: { file-system, locators };
+    import: { file-system, locators, operating-system };
   use testworks;
 
   export testworks-test-suite;
@@ -24,14 +24,13 @@ end library testworks-test-suite;
 define module testworks-test-suite
   use command-line-parser;
   use common-dylan;
-  use file-system,
-    prefix: "fs/";
+  use file-system, prefix: "fs/";
   use format;
   use locators;
+  use operating-system, prefix: "os/";
   use streams;
   use strings;
-  use table-extensions,
-    import: { tabling };
+  use table-extensions, import: { tabling };
   use testworks;
   use %testworks;
 
diff --git a/tests/run.dylan b/tests/run.dylan
index 02451e2..a43edff 100644
--- a/tests/run.dylan
+++ b/tests/run.dylan
@@ -14,6 +14,23 @@ define test test-test-temp-directory/slash-replaced? ()
                locator-name(dir));
 end;
 
+// https://github.com/dylan-lang/testworks/issues/157
+define test test-test-temp-directory/absolute-path ()
+  let dylan = os/environment-variable("DYLAN");
+  block ()
+    // This value must be a relative path.
+    // This test is obviously not thread safe.
+    os/environment-variable("DYLAN") := "dylan/root";
+    let tmp = test-temp-directory();
+    let d1 = subdirectory-locator(tmp, "d1");
+    let f1 = merge-locators(as(<file-locator>, "f1"), tmp);
+    let f2 = write-test-file(f1, content: "x");
+    assert-equal(resolve-locator(f1), resolve-locator(f2));
+  cleanup
+    os/environment-variable("DYLAN") := dylan;
+  end;
+end test;
+
 define test test-write-test-file ()
   let x = write-test-file("x");
   assert-instance?(<file-locator>, x);
diff --git a/tests/suite.dylan b/tests/suite.dylan
index 852dfa2..435dba0 100644
--- a/tests/suite.dylan
+++ b/tests/suite.dylan
@@ -27,6 +27,8 @@ define suite testworks-test-suite ()
   test test-run-tests/suite;
   test test-run-tests/test;
   test test-tags-match?;
+  test test-test-temp-directory/absolute-path;
+  test test-test-temp-directory/slash-replaced?;
   test test-test-temp-directory;
   test test-that-not-implemented-is-not-a-failure;
   test test-that-not-implemented-plus-passed-is-passed;