diff --git a/.github/workflows/run-tests.yml b/.github/workflows/run-tests.yml
index 7c54bbd..bebf1ab 100644
--- a/.github/workflows/run-tests.yml
+++ b/.github/workflows/run-tests.yml
@@ -47,4 +47,4 @@ jobs:
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       run: |
         coverage run setup.py test
-        coveralls
+        coveralls --service=github
diff --git a/src/ufonormalizer/__init__.py b/src/ufonormalizer/__init__.py
index d891773..1f16a99 100644
--- a/src/ufonormalizer/__init__.py
+++ b/src/ufonormalizer/__init__.py
@@ -524,9 +524,9 @@ def _normalizeDictGuideline(guideline):
     # The spec was ambiguous about y=0 or x=0, so don't raise an error here,
     # instead, <x=300 y=0> or <x=0 y=300> are allowed, and the 0 becomes None.
     if angle is None:
-        if x == 0:
+        if x == 0 and y is not None:
             x = None
-        if y == 0:
+        if y == 0 and x is not None:
             y = None
     # either x or y must be defined
     if x is None and y is None:
diff --git a/tests/test_ufonormalizer.py b/tests/test_ufonormalizer.py
index 09dbcd4..4589f80 100644
--- a/tests/test_ufonormalizer.py
+++ b/tests/test_ufonormalizer.py
@@ -710,6 +710,13 @@ def test_normalizeFontInfoPlist_guidelines_vertical_y_is_zero(self):
         _normalizeGlifGuideline(element, writer)
         self.assertEqual(writer.getText(), '<guideline x="100"/>')
 
+    def test_normalizeFontInfoPlist_guidelines_vertical_y_is_zero2(self):
+        # Actually a vertical guide
+        element = ET.fromstring("<guideline y='0'/>")
+        writer = XMLWriter(declaration=None)
+        _normalizeGlifGuideline(element, writer)
+        self.assertEqual(writer.getText(), '<guideline y="0"/>')
+
     def test_normalizeFontInfoPlist_guidelines_horizontal_x_is_zero(self):
         # Actually an horizontal guide
         element = ET.fromstring("<guideline x='0.0' y='100'/>")
@@ -717,6 +724,13 @@ def test_normalizeFontInfoPlist_guidelines_horizontal_x_is_zero(self):
         _normalizeGlifGuideline(element, writer)
         self.assertEqual(writer.getText(), '<guideline y="100"/>')
 
+    def test_normalizeFontInfoPlist_guidelines_horizontal_x_is_zero2(self):
+        # Actually an horizontal guide
+        element = ET.fromstring("<guideline x='0.0'/>")
+        writer = XMLWriter(declaration=None)
+        _normalizeGlifGuideline(element, writer)
+        self.assertEqual(writer.getText(), '<guideline x="0"/>')
+
     def test_normalizeGLIF_lib_defined(self):
         e = '''
         <lib>