diff --git a/frontend/src/component/feature/FeatureStrategy/FeatureStrategyConstraints/EditableConstraint/EditableConstraint.tsx b/frontend/src/component/feature/FeatureStrategy/FeatureStrategyConstraints/EditableConstraint/EditableConstraint.tsx
index 937dc0a034..f70a2cf7f4 100644
--- a/frontend/src/component/feature/FeatureStrategy/FeatureStrategyConstraints/EditableConstraint/EditableConstraint.tsx
+++ b/frontend/src/component/feature/FeatureStrategy/FeatureStrategyConstraints/EditableConstraint/EditableConstraint.tsx
@@ -258,9 +258,19 @@ export const EditableConstraint: FC<Props> = ({
         return null;
     }
 
-    const constraintNameOptions = context.map((context) => {
-        return { key: context.name, label: context.name };
-    });
+    const extantContextFieldNames = context.map((context) => context.name);
+    const contextFieldHasBeenDeleted = !extantContextFieldNames.includes(
+        localConstraint.contextName,
+    );
+
+    const availableContextFieldNames = contextFieldHasBeenDeleted
+        ? [...extantContextFieldNames, localConstraint.contextName].toSorted()
+        : extantContextFieldNames;
+
+    const contextFieldOptions = availableContextFieldNames.map((option) => ({
+        key: option,
+        label: option,
+    }));
 
     return (
         <Container>
@@ -272,7 +282,7 @@ export const EditableConstraint: FC<Props> = ({
                             id='context-field-select'
                             name='contextName'
                             label='Context Field'
-                            options={constraintNameOptions}
+                            options={contextFieldOptions}
                             value={contextName || ''}
                             onChange={(contextField) =>
                                 updateConstraint({
diff --git a/src/lib/features/context/context.ts b/src/lib/features/context/context.ts
index b33d7e71ee..2d719504e1 100644
--- a/src/lib/features/context/context.ts
+++ b/src/lib/features/context/context.ts
@@ -245,7 +245,7 @@ export class ContextController extends Controller {
                     tags: ['Context'],
                     summary: 'Validate a context field',
                     description:
-                        'Check whether the provided data can be used to create a context field. If the data is not valid, ...?',
+                        'Check whether the provided data can be used to create a context field. If the data is not valid, returns a 400 status code with the reason why it is not valid.',
                     operationId: 'validate',
                     requestBody: createRequestSchema('nameSchema'),
                     responses: {
diff --git a/src/lib/features/feature-toggle/feature-toggle-service.ts b/src/lib/features/feature-toggle/feature-toggle-service.ts
index 350c46d3f6..7d4c483c66 100644
--- a/src/lib/features/feature-toggle/feature-toggle-service.ts
+++ b/src/lib/features/feature-toggle/feature-toggle-service.ts
@@ -497,10 +497,6 @@ export class FeatureToggleService {
     async validateConstraint(input: IConstraint): Promise<IConstraint> {
         const constraint = await constraintSchema.validateAsync(input);
         const { operator } = constraint;
-        const contextDefinition = await this.contextFieldStore.get(
-            constraint.contextName,
-        );
-
         if (oneOf(NUM_OPERATORS, operator)) {
             await validateNumber(constraint.value);
         }
@@ -519,20 +515,26 @@ export class FeatureToggleService {
             await validateDate(constraint.value);
         }
 
-        if (
-            contextDefinition?.legalValues &&
-            contextDefinition.legalValues.length > 0
-        ) {
-            const valuesToValidate = oneOf(
-                [...DATE_OPERATORS, ...SEMVER_OPERATORS, ...NUM_OPERATORS],
-                operator,
-            )
-                ? constraint.value
-                : constraint.values;
-            validateLegalValues(
-                contextDefinition.legalValues,
-                valuesToValidate,
+        if (await this.contextFieldStore.exists(constraint.contextName)) {
+            const contextDefinition = await this.contextFieldStore.get(
+                constraint.contextName,
             );
+
+            if (
+                contextDefinition?.legalValues &&
+                contextDefinition.legalValues.length > 0
+            ) {
+                const valuesToValidate = oneOf(
+                    [...DATE_OPERATORS, ...SEMVER_OPERATORS, ...NUM_OPERATORS],
+                    operator,
+                )
+                    ? constraint.value
+                    : constraint.values;
+                validateLegalValues(
+                    contextDefinition.legalValues,
+                    valuesToValidate,
+                );
+            }
         }
 
         return constraint;
diff --git a/src/test/e2e/api/admin/constraints.e2e.test.ts b/src/test/e2e/api/admin/constraints.e2e.test.ts
index bf7c398cac..2e337dec73 100644
--- a/src/test/e2e/api/admin/constraints.e2e.test.ts
+++ b/src/test/e2e/api/admin/constraints.e2e.test.ts
@@ -43,3 +43,25 @@ test('should accept valid constraints', async () => {
         .send({ contextName: 'environment', operator: 'IN', values: ['a'] })
         .expect(204);
 });
+
+test('should allow unknown constraints if their values are valid', async () => {
+    await app.request
+        .post(PATH)
+        .send({
+            contextName: 'not-a-default-context-value',
+            operator: 'NUM_EQ',
+            value: 1,
+        })
+        .expect(204);
+});
+
+test('should block unknown constraints if their values are invalid', async () => {
+    await app.request
+        .post(PATH)
+        .send({
+            contextName: 'not-a-default-context-value',
+            operator: 'IN',
+            value: 1,
+        })
+        .expect(400);
+});