diff --git a/packages/react-reconciler/src/ReactFiberBeginWork.js b/packages/react-reconciler/src/ReactFiberBeginWork.js
index 75da91a5da89d..bd745e02d12a2 100644
--- a/packages/react-reconciler/src/ReactFiberBeginWork.js
+++ b/packages/react-reconciler/src/ReactFiberBeginWork.js
@@ -4037,6 +4037,9 @@ function beginWork(
       );
     }
     case IncompleteFunctionComponent: {
+      if (disableLegacyMode) {
+        break;
+      }
       const Component = workInProgress.type;
       const unresolvedProps = workInProgress.pendingProps;
       const resolvedProps =
diff --git a/packages/react-reconciler/src/ReactFiberCompleteWork.js b/packages/react-reconciler/src/ReactFiberCompleteWork.js
index 04a1c013b075d..51e21b8d2f480 100644
--- a/packages/react-reconciler/src/ReactFiberCompleteWork.js
+++ b/packages/react-reconciler/src/ReactFiberCompleteWork.js
@@ -950,10 +950,15 @@ function completeWork(
   // for hydration.
   popTreeContext(workInProgress);
   switch (workInProgress.tag) {
+    case IncompleteFunctionComponent: {
+      if (disableLegacyMode) {
+        break;
+      }
+      // Fallthrough
+    }
     case LazyComponent:
     case SimpleMemoComponent:
     case FunctionComponent:
-    case IncompleteFunctionComponent:
     case ForwardRef:
     case Fragment:
     case Mode:
diff --git a/packages/react-reconciler/src/getComponentNameFromFiber.js b/packages/react-reconciler/src/getComponentNameFromFiber.js
index d3d2d7dd638a3..6659b14b7f0d0 100644
--- a/packages/react-reconciler/src/getComponentNameFromFiber.js
+++ b/packages/react-reconciler/src/getComponentNameFromFiber.js
@@ -36,6 +36,7 @@ import {
   SimpleMemoComponent,
   LazyComponent,
   IncompleteClassComponent,
+  IncompleteFunctionComponent,
   DehydratedFragment,
   SuspenseListComponent,
   ScopeComponent,