diff --git a/src/harness/loggedIO.ts b/src/harness/loggedIO.ts
index fcc163e77f3..c5d428f3095 100644
--- a/src/harness/loggedIO.ts
+++ b/src/harness/loggedIO.ts
@@ -159,7 +159,7 @@ namespace Playback {
     }
 
     const canonicalizeForHarness = ts.createGetCanonicalFileName(/*caseSensitive*/ false); // This is done so tests work on windows _and_ linux
-    function sanitizeTestFilePath(name: string) {
+    export function sanitizeTestFilePath(name: string) {
         const path = ts.toPath(ts.normalizeSlashes(name.replace(/[\^<>:"|?*%]/g, "_")).replace(/\.\.\//g, "__dotdot/"), "", canonicalizeForHarness);
         if (ts.startsWith(path, "/")) {
             return path.substring(1);
diff --git a/src/harness/rwcRunner.ts b/src/harness/rwcRunner.ts
index 2b4fc7b24e4..9e17aa84b0c 100644
--- a/src/harness/rwcRunner.ts
+++ b/src/harness/rwcRunner.ts
@@ -70,10 +70,11 @@ namespace RWC {
                     opts.options.noEmitOnError = false;
                 });
 
+                let tsconfigFile: IOLogFile;
                 runWithIOLog(ioLog, oldIO => {
                     let fileNames = opts.fileNames;
 
-                    const tsconfigFile = ts.forEach(ioLog.filesRead, f => isTsConfigFile(f) ? f : undefined);
+                    tsconfigFile = ts.forEach(ioLog.filesRead, f => isTsConfigFile(f) ? f : undefined);
                     if (tsconfigFile) {
                         const tsconfigFileContents = getHarnessCompilerInputUnit(tsconfigFile.path);
                         tsconfigFiles.push({ unitName: tsconfigFile.path, content: tsconfigFileContents.content });
@@ -155,6 +156,11 @@ namespace RWC {
                     compilerResult = output.result;
                 });
 
+                if (!tsconfigFile) {
+                    const files = inputFiles.map(f => Playback.sanitizeTestFilePath(f.unitName));
+                    Harness.IO.writeFile(`internal/cases/rwc/${baseName}/read/tsconfig.json`, JSON.stringify({ compilerOptions, files }));
+                }
+
                 function getHarnessCompilerInputUnit(fileName: string): Harness.Compiler.TestFile {
                     const unitName = ts.normalizeSlashes(Harness.IO.resolvePath(fileName));
                     let content: string;