diff --git a/manifest_xml.py b/manifest_xml.py
index 0c2b45e5..64b7fb4e 100644
--- a/manifest_xml.py
+++ b/manifest_xml.py
@@ -1199,6 +1199,8 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
     if '~' in path:
       return '~ not allowed (due to 8.3 filenames on Windows filesystems)'
 
+    path_codepoints = set(path)
+
     # Some filesystems (like Apple's HFS+) try to normalize Unicode codepoints
     # which means there are alternative names for ".git".  Reject paths with
     # these in it as there shouldn't be any reasonable need for them here.
@@ -1222,10 +1224,17 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
         u'\u206F',  # NOMINAL DIGIT SHAPES
         u'\uFEFF',  # ZERO WIDTH NO-BREAK SPACE
     }
-    if BAD_CODEPOINTS & set(path):
+    if BAD_CODEPOINTS & path_codepoints:
       # This message is more expansive than reality, but should be fine.
       return 'Unicode combining characters not allowed'
 
+    # Reject newlines as there shouldn't be any legitmate use for them, they'll
+    # be confusing to users, and they can easily break tools that expect to be
+    # able to iterate over newline delimited lists.  This even applies to our
+    # own code like .repo/project.list.
+    if {'\r', '\n'} & path_codepoints:
+      return 'Newlines not allowed'
+
     # Assume paths might be used on case-insensitive filesystems.
     path = path.lower()
 
diff --git a/tests/test_manifest_xml.py b/tests/test_manifest_xml.py
index eda06968..e78d85c3 100644
--- a/tests/test_manifest_xml.py
+++ b/tests/test_manifest_xml.py
@@ -52,6 +52,9 @@ INVALID_FS_PATHS = (
     'blah/foo~',
     # Block Unicode characters that get normalized out by filesystems.
     u'foo\u200Cbar',
+    # Block newlines.
+    'f\n/bar',
+    'f\r/bar',
 )
 
 # Make sure platforms that use path separators (e.g. Windows) are also
@@ -91,6 +94,11 @@ class ManifestParseTestCase(unittest.TestCase):
       fp.write(data)
     return manifest_xml.XmlManifest(self.repodir, self.manifest_file)
 
+  @staticmethod
+  def encodeXmlAttr(attr):
+    """Encode |attr| using XML escape rules."""
+    return attr.replace('\r', '
').replace('\n', '
')
+
 
 class ManifestValidateFilePaths(unittest.TestCase):
   """Check _ValidateFilePaths helper.
@@ -303,6 +311,7 @@ class IncludeElementTests(ManifestParseTestCase):
   def test_allow_bad_name_from_user(self):
     """Check handling of bad name attribute from the user's input."""
     def parse(name):
+      name = self.encodeXmlAttr(name)
       manifest = self.getXmlManifest(f"""
 <manifest>
   <remote name="default-remote" fetch="http://localhost" />
@@ -327,6 +336,7 @@ class IncludeElementTests(ManifestParseTestCase):
   def test_bad_name_checks(self):
     """Check handling of bad name attribute."""
     def parse(name):
+      name = self.encodeXmlAttr(name)
       # Setup target of the include.
       with open(os.path.join(self.manifest_dir, 'target.xml'), 'w') as fp:
         fp.write(f'<manifest><include name="{name}"/></manifest>')
@@ -408,6 +418,8 @@ class ProjectElementTests(ManifestParseTestCase):
   def test_trailing_slash(self):
     """Check handling of trailing slashes in attributes."""
     def parse(name, path):
+      name = self.encodeXmlAttr(name)
+      path = self.encodeXmlAttr(path)
       return self.getXmlManifest(f"""
 <manifest>
   <remote name="default-remote" fetch="http://localhost" />
@@ -437,6 +449,8 @@ class ProjectElementTests(ManifestParseTestCase):
   def test_toplevel_path(self):
     """Check handling of path=. specially."""
     def parse(name, path):
+      name = self.encodeXmlAttr(name)
+      path = self.encodeXmlAttr(path)
       return self.getXmlManifest(f"""
 <manifest>
   <remote name="default-remote" fetch="http://localhost" />
@@ -453,6 +467,8 @@ class ProjectElementTests(ManifestParseTestCase):
   def test_bad_path_name_checks(self):
     """Check handling of bad path & name attributes."""
     def parse(name, path):
+      name = self.encodeXmlAttr(name)
+      path = self.encodeXmlAttr(path)
       manifest = self.getXmlManifest(f"""
 <manifest>
   <remote name="default-remote" fetch="http://localhost" />