diff --git a/packages/jest/src/builders/jest/jest.impl.ts b/packages/jest/src/builders/jest/jest.impl.ts
index ed22c76327274b..b51fe312049187 100644
--- a/packages/jest/src/builders/jest/jest.impl.ts
+++ b/packages/jest/src/builders/jest/jest.impl.ts
@@ -76,7 +76,10 @@ function run(
   const jestConfig: { globals: any } = require(options.jestConfig);
   const globals = jestConfig.globals || {};
   Object.assign(globals, {
-    'ts-jest': tsJestConfig
+    'ts-jest': {
+      ...(globals['ts-jest'] || {}),
+      ...tsJestConfig
+    }
   });
 
   const config: any = {