diff --git a/src/app/formulaire/definition/form-compute-fixedvar.ts b/src/app/formulaire/definition/form-compute-fixedvar.ts
index 6168991607cff3a6c066e4bcaec1ad521da6f040..873812579511ebd1760355681e4a6bddd4447770 100644
--- a/src/app/formulaire/definition/form-compute-fixedvar.ts
+++ b/src/app/formulaire/definition/form-compute-fixedvar.ts
@@ -54,6 +54,7 @@ export class FormComputeFixedVar extends FormCompute {
     protected reaffectResultComponents() {
         const nub: Nub = this._formBase.currentNub;
         const computedParam: NgParameter = this.getComputedParameter();
+        this.formResult.resetResults(); // to avoid adding fixed parameters more than once (see below)
         this.formResult.addFixedParameters();
         const varParam: NgParameter = this.getVariatedParameter();
 
diff --git a/src/app/formulaire/definition/form-compute.ts b/src/app/formulaire/definition/form-compute.ts
index 3e5683d6e6194fbee4b753a26a12bd095f9c93fd..a9fb302a1bec10ed63469e388f7a0ad615c29b6b 100644
--- a/src/app/formulaire/definition/form-compute.ts
+++ b/src/app/formulaire/definition/form-compute.ts
@@ -27,7 +27,8 @@ export abstract class FormCompute implements Observer {
 
     /**
      * Copies current Nub result into result components for display on page.
-     * Should be called every time the Nub result changes
+     * Should be called every time the Nub result changes.
+     * Must be idempotent.
      */
     protected abstract reaffectResultComponents();