diff --git a/src/mergeClasses.js b/src/mergeClasses.js
index 4e275ac..cba8979 100644
--- a/src/mergeClasses.js
+++ b/src/mergeClasses.js
@@ -1,7 +1,13 @@
 import _ from 'lodash'
 
 export const mergeClasses = (classes, activeNames = []) => {
+
+  if(!classes.default && activeNames.length === 0){
+    classes = { default: classes }
+  }
+  
   const styles = (classes.default && _.cloneDeep(classes.default)) || {}
+  
   activeNames.map((name) => {
     const toMerge = classes[name]
     if (toMerge) {
diff --git a/test/mergeClasses.test.js b/test/mergeClasses.test.js
index 6654f95..1cb11cf 100644
--- a/test/mergeClasses.test.js
+++ b/test/mergeClasses.test.js
@@ -129,3 +129,41 @@ describe('Combine', () => {
     expect(mergeClasses(classes, [])).toEqual(after2)
   })
 })
+
+describe('Combine with optional default ', () => {
+  it('should assume all properties are under the default property when "default" is omitted with no activeNames', () => {
+    const classes = {
+      header: {
+        margin: '0px',
+      },
+      logo: {
+        color: 'blue',
+      },
+    }
+    const after = {
+      header: {
+        margin: '0px',
+      },
+      logo: {
+        color: 'blue',
+      },
+    }
+    expect(mergeClasses(classes)).toEqual(after)
+  })
+
+  it('should not assume properties are nested under default when "default" is omitted but activeNames are present', () => {
+    const classes = {
+      header: {
+        margin: '0px',
+      },
+      logo: {
+        color: 'blue',
+      },
+    }
+    const after = {}
+
+    const names = ['active']
+
+    expect(mergeClasses(classes, names)).toEqual(after)
+  })
+})