diff --git a/pre_commit_hooks/requirements_txt_fixer.py b/pre_commit_hooks/requirements_txt_fixer.py
index 5884394..21c71f4 100644
--- a/pre_commit_hooks/requirements_txt_fixer.py
+++ b/pre_commit_hooks/requirements_txt_fixer.py
@@ -12,10 +12,12 @@ FAIL = 1
 
 class Requirement:
     UNTIL_COMPARISON = re.compile(b'={2,3}|!=|~=|>=?|<=?')
+    VERSION_MATCHER = re.compile(b'(?:={2,3}|!=|~=|>=?|<=?|@)\s*(?P<version>[A-Za-z0-9./:]+)$')
     UNTIL_SEP = re.compile(rb'[^;\s]+')
 
     def __init__(self) -> None:
         self.value: bytes | None = None
+        self.version: str | None = None
         self.comments: list[bytes] = []
 
     @property
@@ -36,6 +38,17 @@ class Requirement:
 
         return name[:m.start()]
 
+    def has_version(self) -> bool:
+        return self.extract_version() is not None
+
+    def extract_version(self):
+        matches = self.VERSION_MATCHER.search(self.value)
+        if matches:
+            self.version = matches.groups()[0].decode()
+        else:
+            self.version = None
+        return self.version
+
     def __lt__(self, requirement: Requirement) -> bool:
         # \n means top of file comment, so always return True,
         # otherwise just do a string comparison with value.
@@ -47,7 +60,7 @@ class Requirement:
         else:
             return self.name < requirement.name
 
-    def is_complete(self) -> bool:
+    def is_complete(self, require_version: bool = False) -> bool:
         return (
             self.value is not None and
             not self.value.rstrip(b'\r\n').endswith(b'\\')
@@ -60,7 +73,7 @@ class Requirement:
             self.value = value
 
 
-def fix_requirements(f: IO[bytes]) -> int:
+def fix_requirements(f: IO[bytes], require_version: bool = False) -> int:
     requirements: list[Requirement] = []
     before = list(f)
     after: list[bytes] = []
@@ -113,33 +126,53 @@ def fix_requirements(f: IO[bytes]) -> int:
         if req.value != b'pkg-resources==0.0.0\n'
     ]
 
+    missing_versions = []
     for requirement in sorted(requirements):
         after.extend(requirement.comments)
         assert requirement.value, requirement.value
         after.append(requirement.value)
+        if require_version and not requirement.has_version():
+            missing_versions.append(requirement.value.decode().strip())
     after.extend(rest)
 
     after_string = b''.join(after)
 
-    if before_string == after_string:
-        return PASS
-    else:
+    # If the version is required but missing, we return FAIL,
+    # but still write the fixes to the file, because the pip install
+    # will work even if the req file is missing versions.
+    # We could block the write if versions are missing, too. This is
+    # something we should discuss in the PR review.
+    outcome = PASS
+
+    if len(missing_versions) > 0:
+        print("Missing versions in:", ", ".join(missing_versions))
+        outcome = FAIL
+
+    if before_string != after_string:
         f.seek(0)
         f.write(after_string)
         f.truncate()
-        return FAIL
+        outcome = FAIL
+
+    return outcome
 
 
 def main(argv: Sequence[str] | None = None) -> int:
     parser = argparse.ArgumentParser()
     parser.add_argument('filenames', nargs='*', help='Filenames to fix')
+    parser.add_argument('-r', '--require_version',
+        required=False,
+        help='Use this to require each requirement to include a version number',
+        action='store_true',
+        default=False
+    )
     args = parser.parse_args(argv)
 
     retv = PASS
 
     for arg in args.filenames:
         with open(arg, 'rb+') as file_obj:
-            ret_for_file = fix_requirements(file_obj)
+            ret_for_file = fix_requirements(file_obj, args.require_version)
 
             if ret_for_file:
                 print(f'Sorting {arg}')
diff --git a/tests/requirements_txt_fixer_test.py b/tests/requirements_txt_fixer_test.py
index b725afa..69a9719 100644
--- a/tests/requirements_txt_fixer_test.py
+++ b/tests/requirements_txt_fixer_test.py
@@ -122,9 +122,18 @@ def test_requirement_object():
     requirement_bar = Requirement()
     requirement_bar.value = b'bar'
 
+    requirement_baz = Requirement()
+    requirement_baz.value = b'baz>=1.2.3'
+
     # This may look redundant, but we need to test both foo.__lt__(bar) and
     # bar.__lt__(foo)
     assert requirement_foo > top_of_file
     assert top_of_file < requirement_foo
     assert requirement_foo > requirement_bar
     assert requirement_bar < requirement_foo
+
+    # Test the version extraction code
+    assert not requirement_foo.has_version()
+    assert not requirement_bar.has_version()
+    assert requirement_baz.has_version()
+    assert requirement_baz.version == '1.2.3'