diff --git a/lib/ai/formula_screen.dart b/lib/ai/formula_screen.dart
index a600de0..8a7467f 100644
--- a/lib/ai/formula_screen.dart
+++ b/lib/ai/formula_screen.dart
@@ -458,21 +458,12 @@ class _FormulaScreenState extends State<FormulaScreen> {
 
   void _solveForVariable(VariableSpec variable) {
     // Check if the formula is already a DerivedFormula
-    if (formula is DerivedFormula) {
-      ScaffoldMessenger.of(context).showSnackBar(
-        const SnackBar(
-          content: Text('Cannot create derived formula from another derived formula'),
-          duration: Duration(seconds: 2),
-        ),
-      );
-      return;
-    }
-
     try {
       // Create a DerivedFormula with this input variable as output
+      var rootFormula = FormulaInterface.getRootFormula(formula);
       final derivedFormula = DerivedFormula(
         outputName: variable.name,
-        originalFormula: formula,
+        originalFormula: rootFormula
       );
 
       // Navigate to the new DerivedFormula screen
diff --git a/lib/formula_models.dart b/lib/formula_models.dart
index c82f39b..b42f037 100644
--- a/lib/formula_models.dart
+++ b/lib/formula_models.dart
@@ -196,11 +196,10 @@ class DerivedFormula implements FormulaInterface {
     return f.input.every( (vs) => vs.unit != "string") && f.output.unit != "string";
   }
 
-  DerivedFormula({required this.outputName, required FormulaInterface originalFormula}) {
+  DerivedFormula({required this.outputName, required this.originalFormula}) {
 
-    this.originalFormula = FormulaInterface.getRootFormula(originalFormula);
 
-    if( !isDerivable(this.originalFormula) ){
+    if( !isDerivable(originalFormula) ){
       throw ArgumentError(
           "Derived formulas are not supported for formulas with string inputs, because we can't solve for them. Original formula: ${originalFormula.toString()}");
     }