diff --git a/.gitignore b/.gitignore
index e146528..66273be 100644
--- a/.gitignore
+++ b/.gitignore
@@ -91,4 +91,6 @@ ENV/
 # Secret files (for credentials used in testing)
 *.secret
 pytooter_clientcred.txt
-pytooter_usercred.txt
\ No newline at end of file
+pytooter_usercred.txtPipfile
+Pipfile.lock
+Pipfile
diff --git a/mastodon/Mastodon.py b/mastodon/Mastodon.py
index 7f0f0fd..a5c05b7 100644
--- a/mastodon/Mastodon.py
+++ b/mastodon/Mastodon.py
@@ -31,6 +31,11 @@ try:
 except ImportError:
     from urlparse import urlparse
 
+try:
+    import magic
+except ImportError:
+    magic = None
+
 ###
 # Version check functions, including decorator and parser
 ###
@@ -1491,7 +1496,7 @@ class Mastodon:
         # Load avatar, if specified
         if not avatar is None:
             if avatar_mime_type is None and os.path.isfile(avatar):
-                avatar_mime_type = mimetypes.guess_type(avatar)[0]
+                avatar_mime_type = guess_type(avatar)
                 avatar = open(avatar, 'rb')
 
             if avatar_mime_type is None:
@@ -1500,7 +1505,7 @@ class Mastodon:
         # Load header, if specified
         if not header is None:
             if header_mime_type is None and os.path.isfile(header):
-                header_mime_type = mimetypes.guess_type(header)[0]
+                header_mime_type = guess_type(header)
                 header = open(header, 'rb')
 
             if header_mime_type is None:
@@ -1720,7 +1725,7 @@ class Mastodon:
         status_post to attach the media file to a toot.
         """
         if mime_type is None and os.path.isfile(media_file):
-            mime_type = mimetypes.guess_type(media_file)[0]
+            mime_type = guess_type(media_file)
             media_file = open(media_file, 'rb')
         elif mime_type and os.path.isfile(media_file):
             media_file = open(media_file, 'rb')
@@ -2531,3 +2536,11 @@ class MastodonRatelimitError(MastodonError):
 class MastodonMalformedEventError(MastodonError):
     """Raised when the server-sent event stream is malformed"""
     pass
+
+def guess_type(media_file):
+    mime_type = None
+    if magic:
+        mime_type = magic.from_file(media_file, mime=True)
+    else:
+        mime_type = mimetypes.guess_type(media_file)[0]
+    return mime_type
diff --git a/setup.py b/setup.py
index e49c26c..009063d 100644
--- a/setup.py
+++ b/setup.py
@@ -13,7 +13,8 @@ setup(name='Mastodon.py',
           'requests', 
           'python-dateutil', 
           'six', 
-          'pytz', 
+          'pytz',
+          'python-magic',
           'decorator>=4.0.0', 
           'http_ece>=1.0.5',
           'cryptography>=1.6.0'