What It Means & How to Fix It in UE5
🧠 Why You’re Seeing This Error
This error means a function from a Blueprint Interface has been changed — but the Blueprints that implement or call that function haven’t updated correctly.
It usually happens when:
- You removed a return value from a Blueprint Interface function
- You renamed or changed the type of a return pin
- A Blueprint that implements the interface hasn’t been recompiled yet
- A Call Interface Function node is still referencing the old signature
💥 Example Error Message
Interface function 'GetHealth' lost its return pins
🛠️ Common Blueprint Scenario
Blueprint Interface Function: GetHealth
→ Originally returned Float: Health
→ Now updated to return Struct: HealthData
[Blueprint A] implements the interface, but its "Call GetHealth" node is outdated.
Result: ❌ Return pin disappears, and compiler shows an error.
✅ How to Fix It in UE5 – Step-by-Step
✔️ 1. Recompile the Interface
- Open the Blueprint Interface
- Click Compile and Save
This updates the function definition across the project.
✔️ 2. Recompile All Blueprints That Use or Implement the Interface
- Open each Blueprint that calls or implements the interface function
- Click Compile
- Replace any broken nodes manually if needed
This forces Unreal to refresh the function signatures and return pins.
✔️ 3. Delete and Re-add the Function Call Node
- Delete the "Call GetHealth" node (or similar)
- Right-click → Add Call to Interface Function → GetHealth
- Reconnect inputs and outputs
This ensures you’re using the most up-to-date version of the function.
✔️ 4. If Using a Parent Blueprint, Recompile That First
- If the Blueprint inherits from another class that implements the interface,
compile the parent class first
✅ Summary: How to Fix “Interface Function Lost Its Return Pins” in UE5
| Cause | Fix |
|---|---|
| Interface function was modified | Recompile the Blueprint Interface and all dependent Blueprints |
| Return value was changed or removed | Replace broken function nodes with updated versions |
| Blueprint not refreshed after change | Compile manually to update all interface links |
