diff --git a/pytest_html/plugin.py b/pytest_html/plugin.py
index d1f5f2d9..49578cba 100644
--- a/pytest_html/plugin.py
+++ b/pytest_html/plugin.py
@@ -14,8 +14,8 @@
 import sys
 import time
 import bisect
-import hashlib
 import warnings
+import re
 
 try:
     from ansi2html import Ansi2HTMLConverter, style
@@ -167,21 +167,17 @@ def __lt__(self, other):
         def create_asset(
             self, content, extra_index, test_index, file_extension, mode="w"
         ):
-
-            hash_key = "".join([self.test_id, str(extra_index), str(test_index)])
-            hash_generator = hashlib.md5()
-            hash_generator.update(hash_key.encode("utf-8"))
-            hex_digest = hash_generator.hexdigest()
-            # 255 is the common max filename length on various filesystems,
-            # we subtract hash length, file extension length and 2 more
-            # characters for the underscore and dot
-            max_length = 255 - len(hex_digest) - len(file_extension) - 2
-            asset_file_name = "{0}_{1}.{2}".format(
-                hash_key[:max_length], hex_digest, file_extension
-            )
+            # 255 is the common max filename length on various filesystems
+            asset_file_name = "{}_{}_{}.{}".format(
+                re.sub(r"[^\w\.]", "_", self.test_id),
+                str(extra_index),
+                str(test_index),
+                file_extension,
+            )[-255:]
             asset_path = os.path.join(
                 os.path.dirname(self.logfile), "assets", asset_file_name
             )
+
             if not os.path.exists(os.path.dirname(asset_path)):
                 os.makedirs(os.path.dirname(asset_path))
 
@@ -217,9 +213,9 @@ def append_extra_html(self, extra, extra_index, test_index):
                     html_div = html.img(src=src)
                 else:
                     if PY3:
-                        content = b64decode(content.encode("utf-8"))
-                    else:
-                        content = b64decode(content)
+                        content = content.encode("utf-8")
+
+                    content = b64decode(content)
                     href = src = self.create_asset(
                         content, extra_index, test_index, extra.get("extension"), "wb"
                     )
diff --git a/testing/test_pytest_html.py b/testing/test_pytest_html.py
index 76bdc839..c7309a40 100644
--- a/testing/test_pytest_html.py
+++ b/testing/test_pytest_html.py
@@ -10,7 +10,6 @@
 import pkg_resources
 import random
 import re
-import hashlib
 
 import pytest
 
@@ -468,13 +467,8 @@ def pytest_runtest_makereport(item, call):
         )
         testdir.makepyfile("def test_pass(): pass")
         result, html = run(testdir)
-        hash_key = "test_extra_text_separated.py::" "test_pass00"
-        hash_generator = hashlib.md5()
-        hash_generator.update(hash_key.encode("utf-8"))
         assert result.ret == 0
-        src = "{0}/{1}".format(
-            "assets", "{0}_{1}.txt".format(hash_key, hash_generator.hexdigest())
-        )
+        src = "assets/test_extra_text_separated.py__test_pass_0_0.txt"
         link = '<a class="text" href="{0}" target="_blank">'.format(src)
         assert link in html
         assert os.path.exists(src)
@@ -501,13 +495,9 @@ def pytest_runtest_makereport(item, call):
         )
         testdir.makepyfile("def test_pass(): pass")
         result, html = run(testdir)
-        hash_key = "test_extra_image_separated.py::test_pass00"
-        hash_generator = hashlib.md5()
-        hash_generator.update(hash_key.encode("utf-8"))
         assert result.ret == 0
-        src = "{0}/{1}".format(
-            "assets",
-            "{0}_{1}.{2}".format(hash_key, hash_generator.hexdigest(), file_extension),
+        src = "assets/test_extra_image_separated.py__test_pass_0_0.{}".format(
+            file_extension
         )
         link = '<a class="image" href="{0}" target="_blank">'.format(src)
         assert link in html
@@ -543,12 +533,8 @@ def test_fail():
         result, html = run(testdir)
 
         for i in range(1, 4):
-            hash_key = "test_extra_image_separated_rerun.py::" "test_fail0{0}".format(i)
-            hash_generator = hashlib.md5()
-            hash_generator.update(hash_key.encode("utf-8"))
-            src = "assets/{0}_{1}.{2}".format(
-                hash_key, hash_generator.hexdigest(), file_extension
-            )
+            asset_name = "test_extra_image_separated_rerun.py__test_fail"
+            src = "assets/{}_0_{}.{}".format(asset_name, i, file_extension)
             link = '<a class="image" href="{0}" target="_blank">'.format(src)
             assert result.ret
             assert link in html
@@ -602,16 +588,36 @@ def {0}():
             )
         )
         result, html = run(testdir)
-
-        hash_key = "test_very_long_test_name.py::{}00".format(test_name)
-        hash_generator = hashlib.md5()
-        hash_generator.update(hash_key.encode("utf-8"))
-        src = "assets/{0}_{1}.png".format(hash_key[:218], hash_generator.hexdigest())
+        file_name = "test_very_long_test_name.py__{}_0_0.png".format(test_name)[-255:]
+        src = "assets/" + file_name
         link = '<a class="image" href="{0}" target="_blank">'.format(src)
         assert result.ret
         assert link in html
         assert os.path.exists(src)
 
+    def test_no_invalid_characters_in_filename(self, testdir):
+        testdir.makeconftest(
+            """
+            import pytest
+            @pytest.hookimpl(hookwrapper=True)
+            def pytest_runtest_makereport(item, call):
+                outcome = yield
+                report = outcome.get_result()
+                if report.when == 'call':
+                    from pytest_html import extras
+                    report.extra = [extras.image('image.png')]
+        """
+        )
+        testdir.makepyfile(
+            """
+            def test_fail():
+                assert False
+        """
+        )
+        run(testdir)
+        for filename in os.listdir("assets"):
+            assert re.search(r'[:\\<>\*\?\|"}{}~]', filename) is None
+
     def test_no_environment(self, testdir):
         testdir.makeconftest(
             """
diff --git a/tox.ini b/tox.ini
index 1489252b..5c6a4fb3 100644
--- a/tox.ini
+++ b/tox.ini
@@ -7,12 +7,13 @@
 envlist = py{27,36,37,py,py3}{,-ansi2html}, flake8, black
 
 [testenv]
-commands = pytest -v -r a {posargs}
+setenv = PYTHONDONTWRITEBYTECODE=1
 deps =
     pytest-xdist
     pytest-rerunfailures
     pytest-mock
     py{27,36,py,py3}-ansi2html: ansi2html
+commands = pytest -v -r a {posargs}
 
 [testenv:flake8]
 skip_install = true