diff --git a/src/__tests__/config.js b/src/__tests__/config.js
index 7fdb1e00..698d7aaf 100644
--- a/src/__tests__/config.js
+++ b/src/__tests__/config.js
@@ -56,6 +56,14 @@ describe('configuration API', () => {
     })
   })
 
+  test('configuring only DTL options preserves previously set RTL options', () => {
+    configure({reactStrictMode: true})
+    configure({testIdAttribute: 'not-data-testid'})
+
+    expect(getConfig().reactStrictMode).toBe(true)
+    expect(getConfig().testIdAttribute).toBe('not-data-testid')
+  })
+
   test('configure can set DTL and RTL options at once', () => {
     const testIdAttribute = 'not-data-testid'
     configure({testIdAttribute, reactStrictMode: true})
diff --git a/src/config.js b/src/config.js
index dc8a5035..4a5c0ada 100644
--- a/src/config.js
+++ b/src/config.js
@@ -25,9 +25,11 @@ function configure(newConfig) {
 
   configureDTL(configForDTL)
 
-  configForRTL = {
-    ...configForRTL,
-    reactStrictMode,
+  if (reactStrictMode !== undefined) {
+    configForRTL = {
+      ...configForRTL,
+      reactStrictMode,
+    }
   }
 }