diff --git a/drafts/v1.0/MetronInfo.xsd b/drafts/v1.0/MetronInfo.xsd
index f913ca7..4d45091 100644
--- a/drafts/v1.0/MetronInfo.xsd
+++ b/drafts/v1.0/MetronInfo.xsd
@@ -16,7 +16,7 @@
             <xs:element name="Prices" type="pricesType" minOccurs="0" />
             <xs:element name="CoverDate" type="xs:date" minOccurs="0" />
             <xs:element name="StoreDate" type="xs:date" minOccurs="0" />
-            <xs:element name="PageCount" type="xs:int" minOccurs="0" default="0" />
+            <xs:element name="PageCount" type="xs:nonNegativeInteger" minOccurs="0" default="0" />
             <xs:element name="Notes" type="xs:string" minOccurs="0" />
             <xs:element name="Genres" type="genresType" minOccurs="0" />
             <xs:element name="Tags" type="tagsType" minOccurs="0" />
@@ -92,7 +92,7 @@
         <xs:all>
             <xs:element name="Name" type="xs:string" />
             <xs:element name="SortName" type="xs:string" minOccurs="0" />
-            <xs:element name="Volume" type="xs:int" minOccurs="0" />
+            <xs:element name="Volume" type="xs:nonNegativeInteger" minOccurs="0" />
             <xs:element name="Format" type="formatType" minOccurs="0" />
             <xs:element name="StartYear" type="xs:gYear" minOccurs="0" />
             <xs:element name="IssueCount" type="xs:positiveInteger" minOccurs="0" />
diff --git a/tests/test.py b/tests/test.py
index 8a39df7..9e06ebc 100644
--- a/tests/test.py
+++ b/tests/test.py
@@ -8,19 +8,45 @@
 
 
 @pytest.mark.parametrize(
-    ("xsd", "xml"), [(TEST_XSD, TEST_FILES_PATH / "valid.xml")], ids=["valid_xml"]
+    ("xsd", "xml"),
+    [
+        (TEST_XSD, TEST_FILES_PATH / "valid.xml"),
+        (
+            TEST_XSD,
+            '<?xml version="1.0" encoding="UTF-8"?><MetronInfo xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">'
+            "<Series><Name>Foo</Name></Series><Number /><PageCount>0</PageCount></MetronInfo>",
+        ),
+        (
+            TEST_XSD,
+            '<?xml version="1.0" encoding="UTF-8"?><MetronInfo xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">'
+            "<Series><Name>Foo</Name><Volume>0</Volume></Series><Number /></MetronInfo>",
+        ),
+    ],
+    ids=["valid_xml", "zero_page_count", "volume_zero"],
 )
-def test_valid(xsd, xml) -> None:
+def test_valid(xsd: Path, xml: Path | str) -> None:
     schema = XMLSchema11(xsd)
     schema.validate(xml)
 
 
 @pytest.mark.parametrize(
     ("xsd", "xml"),
-    [(TEST_XSD, TEST_FILES_PATH / "dup_primary_attr.xml")],
-    ids=["dup_primary_attr_xml"],
+    [
+        (TEST_XSD, TEST_FILES_PATH / "dup_primary_attr.xml"),
+        (
+            TEST_XSD,
+            '<?xml version="1.0" encoding="UTF-8"?><MetronInfo xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">'
+            "<Series><Name>Foo</Name></Series><Number /><PageCount>-1</PageCount></MetronInfo>",
+        ),
+        (
+            TEST_XSD,
+            '<?xml version="1.0" encoding="UTF-8"?><MetronInfo xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">'
+            "<Series><Name>Foo</Name><Volume>-1</Volume></Series><Number /></MetronInfo>",
+        ),
+    ],
+    ids=["dup_primary_attr_xml", "negative_page_count", "negative_volume"],
 )
-def test_invalid(xsd, xml) -> None:
+def test_invalid(xsd: Path, xml: Path | str) -> None:
     schema = XMLSchema11(xsd)
     with pytest.raises(XMLSchemaValidationError):
         schema.validate(xml)