diff --git a/pre_commit_hooks/requirements_txt_fixer.py b/pre_commit_hooks/requirements_txt_fixer.py
index 6dcf8d0..dcfa8d5 100644
--- a/pre_commit_hooks/requirements_txt_fixer.py
+++ b/pre_commit_hooks/requirements_txt_fixer.py
@@ -61,6 +61,9 @@ def fix_requirements(f):
         elif line.startswith(b'#') or line.strip() == b'':
             requirement.comments.append(line)
         else:
+            # Automatically fix 'package=version' to 'package==version'
+            if b'=' in line and b'==' not in line and b'egg=' not in line:
+                line = line.replace(b'=', b'==')
             requirement.value = line
 
     # if a file ends in a comment, preserve it at the end
diff --git a/tests/requirements_txt_fixer_test.py b/tests/requirements_txt_fixer_test.py
index 437cebd..38f75df 100644
--- a/tests/requirements_txt_fixer_test.py
+++ b/tests/requirements_txt_fixer_test.py
@@ -30,6 +30,7 @@ from pre_commit_hooks.requirements_txt_fixer import Requirement
         ),
         (b'bar\npkg-resources==0.0.0\nfoo\n', FAIL, b'bar\nfoo\n'),
         (b'foo\npkg-resources==0.0.0\nbar\n', FAIL, b'bar\nfoo\n'),
+        (b'foo=1\n', FAIL, b'foo==1\n'),
     ),
 )
 def test_integration(input_s, expected_retval, output, tmpdir):