diff --git a/src/rules/immutable-data.ts b/src/rules/immutable-data.ts
index dbdf3ba1f..1010ffaba 100644
--- a/src/rules/immutable-data.ts
+++ b/src/rules/immutable-data.ts
@@ -110,13 +110,13 @@ const schema: JSONSchema4[] = [
 /**
  * The default options for the rule.
  */
-const defaultOptions: RawOptions = [
+const defaultOptions = [
   {
     ignoreClasses: false,
     ignoreImmediateMutation: true,
     ignoreNonConstDeclarations: false,
   },
-];
+] satisfies RawOptions;
 
 /**
  * The possible error messages.
@@ -227,10 +227,8 @@ function checkAssignmentExpression(
 ): RuleResult<keyof typeof errorMessages, RawOptions> {
   const options = upgradeRawOverridableOptions(rawOptions[0]);
   const rootNode = findRootIdentifier(node.left) ?? node.left;
-  const optionsToUse = getCoreOptions<CoreOptions, Options>(
-    rootNode,
-    context,
-    options,
+  const optionsToUse = getOptionsWithDefaults(
+    getCoreOptions<CoreOptions, Options>(rootNode, context, options),
   );
 
   if (optionsToUse === null) {
@@ -306,10 +304,8 @@ function checkUnaryExpression(
 ): RuleResult<keyof typeof errorMessages, RawOptions> {
   const options = upgradeRawOverridableOptions(rawOptions[0]);
   const rootNode = findRootIdentifier(node.argument) ?? node.argument;
-  const optionsToUse = getCoreOptions<CoreOptions, Options>(
-    rootNode,
-    context,
-    options,
+  const optionsToUse = getOptionsWithDefaults(
+    getCoreOptions<CoreOptions, Options>(rootNode, context, options),
   );
 
   if (optionsToUse === null) {
@@ -384,10 +380,8 @@ function checkUpdateExpression(
 ): RuleResult<keyof typeof errorMessages, RawOptions> {
   const options = upgradeRawOverridableOptions(rawOptions[0]);
   const rootNode = findRootIdentifier(node.argument) ?? node.argument;
-  const optionsToUse = getCoreOptions<CoreOptions, Options>(
-    rootNode,
-    context,
-    options,
+  const optionsToUse = getOptionsWithDefaults(
+    getCoreOptions<CoreOptions, Options>(rootNode, context, options),
   );
 
   if (optionsToUse === null) {
@@ -533,6 +527,22 @@ function isInChainCallAndFollowsNew(
   return false;
 }
 
+/**
+ * Add the default options to the given options.
+ */
+function getOptionsWithDefaults(
+  options: Readonly<Options> | null,
+): Options | null {
+  if (options === null) {
+    return null;
+  }
+
+  return {
+    ...defaultOptions[0],
+    ...options,
+  };
+}
+
 /**
  * Check if the given node violates this rule.
  */
@@ -543,10 +553,8 @@ function checkCallExpression(
 ): RuleResult<keyof typeof errorMessages, RawOptions> {
   const options = upgradeRawOverridableOptions(rawOptions[0]);
   const rootNode = findRootIdentifier(node.callee) ?? node.callee;
-  const optionsToUse = getCoreOptions<CoreOptions, Options>(
-    rootNode,
-    context,
-    options,
+  const optionsToUse = getOptionsWithDefaults(
+    getCoreOptions<CoreOptions, Options>(rootNode, context, options),
   );
 
   if (optionsToUse === null) {
diff --git a/src/rules/prefer-immutable-types.ts b/src/rules/prefer-immutable-types.ts
index 47c32bb78..c0d654b54 100644
--- a/src/rules/prefer-immutable-types.ts
+++ b/src/rules/prefer-immutable-types.ts
@@ -278,7 +278,7 @@ const schema: JSONSchema4[] = [
 /**
  * The default options for the rule.
  */
-const defaultOptions: RawOptions = [
+const defaultOptions = [
   {
     enforcement: Immutability.Immutable,
     ignoreInferredTypes: false,
@@ -308,7 +308,7 @@ const defaultOptions: RawOptions = [
       ],
     },
   },
-];
+] satisfies RawOptions;
 
 /**
  * The possible error messages.
@@ -496,10 +496,8 @@ function getParameterTypeViolations(
       const parameterProperty = isTSParameterProperty(param);
       const actualParam = parameterProperty ? param.parameter : param;
 
-      const optionsToUse = getCoreOptions<CoreOptions, Options>(
-        param,
-        context,
-        options,
+      const optionsToUse = getOptionsWithDefaults(
+        getCoreOptions<CoreOptions, Options>(param, context, options),
       );
 
       if (optionsToUse === null) {
@@ -637,11 +635,13 @@ function getReturnTypeViolations(
   options: Readonly<Options>,
 ): Descriptor[] {
   function getOptions(type: Type, typeNode: TypeNode | null) {
-    const optionsToUse = getCoreOptionsForType<CoreOptions, Options>(
-      type,
-      typeNode,
-      context,
-      options,
+    const optionsToUse = getOptionsWithDefaults(
+      getCoreOptionsForType<CoreOptions, Options>(
+        type,
+        typeNode,
+        context,
+        options,
+      ),
     );
 
     if (optionsToUse === null) {
@@ -824,6 +824,22 @@ function getReturnTypeViolations(
   ];
 }
 
+/**
+ * Add the default options to the given options.
+ */
+function getOptionsWithDefaults(
+  options: Readonly<Options> | null,
+): Options | null {
+  if (options === null) {
+    return null;
+  }
+
+  return {
+    ...defaultOptions[0],
+    ...options,
+  };
+}
+
 /**
  * Check if the given function node violates this rule.
  */
@@ -854,10 +870,8 @@ function checkVariable(
   rawOptions: Readonly<RawOptions>,
 ): RuleResult<keyof typeof errorMessages, RawOptions> {
   const options = upgradeRawOverridableOptions(rawOptions[0]);
-  const optionsToUse = getCoreOptions<CoreOptions, Options>(
-    node,
-    context,
-    options,
+  const optionsToUse = getOptionsWithDefaults(
+    getCoreOptions<CoreOptions, Options>(node, context, options),
   );
 
   if (optionsToUse === null) {