diff --git a/src/js/babel.js b/src/js/babel.js
index 6f48b5f..b49127e 100644
--- a/src/js/babel.js
+++ b/src/js/babel.js
@@ -80,7 +80,7 @@ export default class BabelCompiler extends SimpleCompilerBase {
       filename: filePath,
       ast: false,
       babelrc: false
-    }, compilerContext);
+    });
 
     let useCoverage = false;
     if ('coverage' in opts) {
diff --git a/src/js/typescript.js b/src/js/typescript.js
index daa759c..e6c6a32 100644
--- a/src/js/typescript.js
+++ b/src/js/typescript.js
@@ -112,13 +112,14 @@ export default class TypeScriptCompiler extends SimpleCompilerBase {
           babelOpts.sourceMaps = true;
         }
 
-        this.babel.compilerOptions = babelOpts;
+        this.babelOpts = babelOpts;
       }
 
-      let babelOutput = this.babel.compileSync(code, filePath, {
+      this.babel.compilerOptions = Object.assign({}, this.babelOpts, {
         // babel API wants sourceMap as an object or a path. let's not touch the disk.
         inputSourceMap: sourceMaps ? JSON.parse(sourceMaps) : null,
       });
+      let babelOutput = this.babel.compileSync(code, filePath, {});
 
       // babel-transformed, potentially instrumented code
       code = babelOutput.code;