diff --git a/source/blender/compositor/realtime_compositor/intern/multi_function_procedure_operation.cc b/source/blender/compositor/realtime_compositor/intern/multi_function_procedure_operation.cc
index 3b944b7dc8a..c1c7a3f93d8 100644
--- a/source/blender/compositor/realtime_compositor/intern/multi_function_procedure_operation.cc
+++ b/source/blender/compositor/realtime_compositor/intern/multi_function_procedure_operation.cc
@@ -172,14 +172,17 @@ Vector<mf::Variable *> MultiFunctionProcedureOperation::get_input_variables(DNod
       continue;
     }
 
-    /* Get the output linked to the input. If it is null, that means the input is unlinked and we
-     * generate a constant variable for it. */
-    const DOutputSocket output = get_output_linked_to_input(input);
-    if (!output) {
-      input_variables.append(this->get_constant_input_variable(input));
+    /* The origin socket is an input, that means the input is unlinked and we generate a constant
+     * variable for it. */
+    const DSocket origin = get_input_origin_socket(input);
+    if (origin->is_input()) {
+      input_variables.append(this->get_constant_input_variable(DInputSocket(origin)));
       continue;
     }
 
+    /* Otherwise, the origin socket is an output, which means it is linked. */
+    const DOutputSocket output = DOutputSocket(origin);
+
     /* If the origin node is part of the multi-function procedure operation, then the output has an
      * existing variable for it. */
     if (compile_unit_.contains(output.node())) {