diff --git a/src/optimization/CasADiIterCallback.h b/src/optimization/CasADiIterCallback.h
index fa8e9240..a90563ca 100644
--- a/src/optimization/CasADiIterCallback.h
+++ b/src/optimization/CasADiIterCallback.h
@@ -14,7 +14,7 @@ class CasADiIterCallback : public Callback {
   ~CasADiIterCallback() override {}
 
   // Number of inputs and outputs
-  casadi_int get_n_in() override { return 5;}
+  casadi_int get_n_in() override { return 4;}
   casadi_int get_n_out() override { return 1;}
 
   // Initialize the object