diff --git a/fragment/java/android/support/v4/app/Fragment.java b/fragment/java/android/support/v4/app/Fragment.java
index 881c2b4..06d0b1e 100644
--- a/fragment/java/android/support/v4/app/Fragment.java
+++ b/fragment/java/android/support/v4/app/Fragment.java
@@ -2150,6 +2150,9 @@
     }
 
     void instantiateChildFragmentManager() {
+        if (mHost == null) {
+            throw new IllegalStateException("Fragment has not been attached yet.");
+        }
         mChildFragmentManager = new FragmentManagerImpl();
         mChildFragmentManager.attachController(mHost, new FragmentContainer() {
             @Override