diff --git a/source/blender/compositor/COM_multi_function_procedure_operation.hh b/source/blender/compositor/COM_multi_function_procedure_operation.hh
index abba7d3d489..0d505a2d0e9 100644
--- a/source/blender/compositor/COM_multi_function_procedure_operation.hh
+++ b/source/blender/compositor/COM_multi_function_procedure_operation.hh
@@ -110,7 +110,8 @@ class MultiFunctionProcedureOperation : public PixelOperation {
 
   /* Convert the given variable to the given expected type. This is done by adding an implicit
    * conversion function whose output variable will be returned. If no conversion is needed, the
-   * given variable is returned as is. */
+   * given variable is returned as is. If conversion is not possible, a fallback default variable
+   * will b returned. */
   mf::Variable *convert_variable(mf::Variable *variable, const mf::DataType expected_type);
 
   /* Returns true if the operation operates on single values, that is, all of its inputs are single
diff --git a/source/blender/compositor/intern/multi_function_procedure_operation.cc b/source/blender/compositor/intern/multi_function_procedure_operation.cc
index eeef7546380..a4504945214 100644
--- a/source/blender/compositor/intern/multi_function_procedure_operation.cc
+++ b/source/blender/compositor/intern/multi_function_procedure_operation.cc
@@ -444,6 +444,7 @@ void MultiFunctionProcedureOperation::populate_operation_result(DOutputSocket ou
 mf::Variable *MultiFunctionProcedureOperation::convert_variable(mf::Variable *variable,
                                                                 const mf::DataType expected_type)
 {
+  /* Conversion not needed. */
   const mf::DataType variable_type = variable->data_type();
   if (variable_type == expected_type) {
     return variable;
@@ -453,6 +454,16 @@ mf::Variable *MultiFunctionProcedureOperation::convert_variable(mf::Variable *va
   const mf::MultiFunction *function = conversion_table.get_conversion_multi_function(
       variable_type, expected_type);
 
+  /* Conversion is not possible, return a default variable instead. */
+  if (!function) {
+    const mf::MultiFunction &constant_function =
+        procedure_.construct_function<mf::CustomMF_GenericConstant>(
+            expected_type.single_type(), expected_type.single_type().default_value(), false);
+    mf::Variable *constant_variable = procedure_builder_.add_call<1>(constant_function)[0];
+    implicit_variables_.append(constant_variable);
+    return constant_variable;
+  }
+
   mf::Variable *converted_variable = procedure_builder_.add_call<1>(*function, {variable})[0];
   implicit_variables_.append(converted_variable);
   return converted_variable;