diff --git a/src/index.js b/src/index.js
index e7bdf72..a6357ad 100644
--- a/src/index.js
+++ b/src/index.js
@@ -15,13 +15,13 @@ export default function(file, acceptedFiles) {
       ? acceptedFiles
       : acceptedFiles.split(',')
     const fileName = file.name || ''
-    const mimeType = file.type || ''
+    const mimeType = (file.type || '').toLowerCase()
     const baseMimeType = mimeType.replace(/\/.*$/, '')
 
     return acceptedFilesArray.some(type => {
-      const validType = type.trim()
+      const validType = type.trim().toLowerCase()
       if (validType.charAt(0) === '.') {
-        return fileName.toLowerCase().endsWith(validType.toLowerCase())
+        return fileName.toLowerCase().endsWith(validType)
       } else if (validType.endsWith('/*')) {
         // This is something like a image/* mime type
         return baseMimeType === validType.replace(/\/.*$/, '')
diff --git a/test/index.js b/test/index.js
index 502ba6e..53afede 100644
--- a/test/index.js
+++ b/test/index.js
@@ -286,4 +286,25 @@ describe('accept', () => {
       )
     ).toBe(false)
   })
+
+  it('should check MIME types in a case insensitive way', () => {
+    expect(
+      accept(
+        {
+          name: 'testfile.xlsm',
+          type: 'application/vnd.ms-excel.sheet.macroenabled.12'
+        },
+        ['application/vnd.ms-excel.sheet.macroEnabled.12']
+      )
+    ).toBe(true)
+    expect(
+      accept(
+        {
+          name: 'testfile.xlsm',
+          type: 'application/vnd.ms-excel.sheet.macroEnabled.12'
+        },
+        ['application/vnd.ms-excel.sheet.macroenabled.12']
+      )
+    ).toBe(true)
+  })
 })