diff --git a/platform/projectModel-api/src/com/intellij/openapi/roots/OrderRootsEnumerator.java b/platform/projectModel-api/src/com/intellij/openapi/roots/OrderRootsEnumerator.java
index 67e74e9f9bae..6139af8868ba 100644
--- a/platform/projectModel-api/src/com/intellij/openapi/roots/OrderRootsEnumerator.java
+++ b/platform/projectModel-api/src/com/intellij/openapi/roots/OrderRootsEnumerator.java
@@ -60,6 +60,7 @@ public interface OrderRootsEnumerator {
    * option is used
    * @return this instance
    */
+  @NotNull
   OrderRootsEnumerator usingCache();
 
   /**
@@ -69,6 +70,7 @@ public interface OrderRootsEnumerator {
    *
    * @return this instance
    */
+  @NotNull
   OrderRootsEnumerator withoutSelfModuleOutput();
 
   /**
@@ -77,5 +79,6 @@ public interface OrderRootsEnumerator {
    * @param provider function to evaluate roots for an order entry
    * @return this instance
    */
+  @NotNull
   OrderRootsEnumerator usingCustomRootProvider(@NotNull NotNullFunction<OrderEntry, VirtualFile[]> provider);
 }
diff --git a/platform/projectModel-impl/src/com/intellij/openapi/roots/impl/OrderRootsEnumeratorImpl.java b/platform/projectModel-impl/src/com/intellij/openapi/roots/impl/OrderRootsEnumeratorImpl.java
index 82445988e00d..1f26661f68d1 100644
--- a/platform/projectModel-impl/src/com/intellij/openapi/roots/impl/OrderRootsEnumeratorImpl.java
+++ b/platform/projectModel-impl/src/com/intellij/openapi/roots/impl/OrderRootsEnumeratorImpl.java
@@ -189,18 +189,21 @@ public class OrderRootsEnumeratorImpl implements OrderRootsEnumerator {
     list.addVirtualFiles(getRoots());
   }
 
+  @NotNull
   @Override
   public OrderRootsEnumerator usingCache() {
     myUsingCache = true;
     return this;
   }
 
+  @NotNull
   @Override
   public OrderRootsEnumerator withoutSelfModuleOutput() {
     myWithoutSelfModuleOutput = true;
     return this;
   }
 
+  @NotNull
   @Override
   public OrderRootsEnumerator usingCustomRootProvider(@NotNull NotNullFunction<OrderEntry, VirtualFile[]> provider) {
     myCustomRootProvider = provider;