diff --git a/rsconcept/frontend/src/dialogs/DlgEditOperation/DlgEditOperation.tsx b/rsconcept/frontend/src/dialogs/DlgEditOperation/DlgEditOperation.tsx
index 079c287b..7c019cb5 100644
--- a/rsconcept/frontend/src/dialogs/DlgEditOperation/DlgEditOperation.tsx
+++ b/rsconcept/frontend/src/dialogs/DlgEditOperation/DlgEditOperation.tsx
@@ -95,7 +95,7 @@ function DlgEditOperation({ hideWindow, oss, target, onSubmit }: DlgEditOperatio
   }, [schemasIDs, needPreload, cache]);
 
   useEffect(() => {
-    if (cache.loading || schemas.length !== schemasIDs.length) {
+    if (cache.loading || schemas.length !== schemasIDs.length || schemas.length === 0) {
       return;
     }
     setSubstitutions(prev =>
@@ -114,7 +114,7 @@ function DlgEditOperation({ hideWindow, oss, target, onSubmit }: DlgEditOperatio
   }, [schemasIDs, schemas, cache.loading, getSchemaByCst]);
 
   useEffect(() => {
-    if (cache.loading || schemas.length !== schemasIDs.length) {
+    if (cache.loading || schemas.length !== schemasIDs.length || schemas.length === 0) {
       return;
     }
     const validator = new SubstitutionValidator(schemas, substitutions);
diff --git a/rsconcept/frontend/src/dialogs/DlgEditOperation/TabSynthesis.tsx b/rsconcept/frontend/src/dialogs/DlgEditOperation/TabSynthesis.tsx
index ac896a62..af6933ee 100644
--- a/rsconcept/frontend/src/dialogs/DlgEditOperation/TabSynthesis.tsx
+++ b/rsconcept/frontend/src/dialogs/DlgEditOperation/TabSynthesis.tsx
@@ -44,7 +44,7 @@ function TabSynthesis({
           disabled
           value={validationText}
           rows={4}
-          style={{ borderColor: isCorrect ? undefined : APP_COLORS.fgRed }}
+          style={{ borderColor: isCorrect ? undefined : APP_COLORS.fgRed, borderWidth: isCorrect ? undefined : '2px' }}
         />
       </div>
     </DataLoader>
diff --git a/rsconcept/frontend/src/models/RSFormLoader.ts b/rsconcept/frontend/src/models/RSFormLoader.ts
index e9ad37fd..9b6dd30b 100644
--- a/rsconcept/frontend/src/models/RSFormLoader.ts
+++ b/rsconcept/frontend/src/models/RSFormLoader.ts
@@ -75,6 +75,7 @@ export class RSFormLoader {
     const order = this.graph.topologicalOrder();
     order.forEach(cstID => {
       const cst = this.cstByID.get(cstID)!;
+      cst.schema = this.schema.id;
       cst.status = inferStatus(cst.parse.status, cst.parse.valueClass);
       cst.is_template = inferTemplate(cst.definition_formal);
       cst.cst_class = inferClass(cst.cst_type, cst.is_template);
diff --git a/rsconcept/frontend/src/models/ossAPI.ts b/rsconcept/frontend/src/models/ossAPI.ts
index 7559b084..24e4f30b 100644
--- a/rsconcept/frontend/src/models/ossAPI.ts
+++ b/rsconcept/frontend/src/models/ossAPI.ts
@@ -70,9 +70,10 @@ export class SubstitutionValidator {
   constructor(schemas: IRSForm[], substitutions: ICstSubstitute[]) {
     this.schemas = schemas;
     this.substitutions = substitutions;
-    if (this.substitutions.length === 0) {
+    if (schemas.length === 0 || substitutions.length === 0) {
       return;
     }
+
     schemas.forEach(schema => {
       this.schemaByID.set(schema.id, schema);
       this.mapping.set(schema.id, {});
diff --git a/rsconcept/frontend/src/models/rsform.ts b/rsconcept/frontend/src/models/rsform.ts
index 7da75f9d..1f7c2e1b 100644
--- a/rsconcept/frontend/src/models/rsform.ts
+++ b/rsconcept/frontend/src/models/rsform.ts
@@ -65,7 +65,6 @@ export interface TermForm {
  */
 export interface IConstituentaMeta {
   id: ConstituentaID;
-  schema: LibraryItemID;
   alias: string;
   convention: string;
   cst_type: CstType;
@@ -101,6 +100,9 @@ export interface IConstituentaData extends IConstituentaMeta {
  * Represents Constituenta.
  */
 export interface IConstituenta extends IConstituentaData {
+  /** {@link LibraryItemID} of this {@link IConstituenta}. */
+  schema: LibraryItemID;
+
   /** {@link CstClass} of this {@link IConstituenta}. */
   cst_class: CstClass;
   /** {@link ExpressionStatus} of this {@link IConstituenta}. */
@@ -135,7 +137,7 @@ export interface IConstituenta extends IConstituentaData {
 /**
  * Represents {@link IConstituenta} reference.
  */
-export interface IConstituentaReference extends Pick<IConstituentaMeta, 'id' | 'schema'> {}
+export interface IConstituentaReference extends Pick<IConstituenta, 'id' | 'schema'> {}
 
 /**
  * Represents Constituenta list.