diff --git a/src/utils/__tests__/__snapshots__/renderSchema.spec.ts.snap b/src/utils/__tests__/__snapshots__/renderSchema.spec.ts.snap
index c7158128..0077a803 100644
--- a/src/utils/__tests__/__snapshots__/renderSchema.spec.ts.snap
+++ b/src/utils/__tests__/__snapshots__/renderSchema.spec.ts.snap
@@ -25,7 +25,6 @@ Array [
                     "type": "string",
                   },
                 },
-                "type": "object",
               },
               Object {
                 "properties": Object {
@@ -33,7 +32,6 @@ Array [
                     "type": "string",
                   },
                 },
-                "type": "object",
               },
             ],
             "type": "object",
@@ -63,7 +61,6 @@ Array [
                 "type": "string",
               },
             },
-            "type": "object",
           },
           Object {
             "properties": Object {
@@ -71,7 +68,6 @@ Array [
                 "type": "string",
               },
             },
-            "type": "object",
           },
         ],
         "type": "object",
diff --git a/src/utils/__tests__/renderSchema.spec.ts b/src/utils/__tests__/renderSchema.spec.ts
index 4c7b7cbd..a77a8c18 100644
--- a/src/utils/__tests__/renderSchema.spec.ts
+++ b/src/utils/__tests__/renderSchema.spec.ts
@@ -10,19 +10,36 @@ jest.mock('../generateId', () => ({
 
 describe('renderSchema util', () => {
   it.each([
-    ['default-schema.json', ''],
-    ['ref/original.json', 'ref/resolved.json'],
-    ['combiner-schema.json', ''],
-    ['array-of-objects.json', ''],
-    ['array-of-refs.json', ''],
-    ['array-of-allofs.json', ''],
-    ['tickets.schema.json', ''],
-  ])('should match %s', (schema, dereferenced) => {
+    'default-schema.json',
+    'ref/original.json',
+    'combiner-schema.json',
+    'array-of-objects.json',
+    'array-of-refs.json',
+    'array-of-allofs.json',
+    'tickets.schema.json',
+  ])('should match %s', schema => {
     expect(
       Array.from(renderSchema(JSON.parse(fs.readFileSync(path.resolve(BASE_PATH, schema), 'utf8')))),
     ).toMatchSnapshot();
   });
 
+  it.each([
+    'default-schema.json',
+    'ref/original.json',
+    'combiner-schema.json',
+    'array-of-objects.json',
+    'array-of-refs.json',
+    'array-of-allofs.json',
+    'tickets.schema.json',
+  ])('should not mutate original object %s', schema => {
+    const content = fs.readFileSync(path.resolve(BASE_PATH, schema), 'utf8');
+    const input = JSON.parse(content);
+
+    Array.from(renderSchema(input));
+
+    expect(input).toStrictEqual(JSON.parse(content));
+  });
+
   it('given schema with complex types, throws', () => {
     expect(() =>
       Array.from(
diff --git a/src/utils/renderSchema.ts b/src/utils/renderSchema.ts
index d7c977e1..c5adbe88 100644
--- a/src/utils/renderSchema.ts
+++ b/src/utils/renderSchema.ts
@@ -104,10 +104,13 @@ export const renderSchema: Walker = function*(schema, level = 0, meta = { path:
       if (node.properties !== undefined) {
         for (const [i, property] of node.properties.entries()) {
           if ('type' in node) {
-            property.type = property.type || node.type;
+            node.properties[i] = {
+              ...property,
+              type: property.type || node.type,
+            };
           }
 
-          yield* renderSchema(property, level + 1, {
+          yield* renderSchema(node.properties[i], level + 1, {
             ...(i !== 0 && { divider: DIVIDERS[node.combiner] }),
             path: [...path, node.combiner, i],
           });
diff --git a/src/utils/walk.ts b/src/utils/walk.ts
index 88c1a6c2..b6432429 100644
--- a/src/utils/walk.ts
+++ b/src/utils/walk.ts
@@ -27,10 +27,11 @@ function processNode(node: JSONSchema4): SchemaNode | void {
   const type = node.type || inferType(node);
 
   if (combiner) {
+    const properties = node[combiner];
     return {
       id: generateId(),
       combiner,
-      properties: node[combiner],
+      properties: Array.isArray(properties) ? properties.slice() : properties,
       annotations: getAnnotations(node),
       ...(type !== undefined && { type }),
     } as ICombinerNode;