diff --git a/Tests/test_file_xbm.py b/Tests/test_file_xbm.py
index 2cf8d28e7e1..3a0729c5bce 100644
--- a/Tests/test_file_xbm.py
+++ b/Tests/test_file_xbm.py
@@ -110,6 +110,10 @@ def test_invalid_file() -> None:
     with pytest.raises(SyntaxError):
         XbmImagePlugin.XbmImageFile(invalid_file)
 
+    b = BytesIO(b"#define basic_width invalidwidth")
+    with pytest.raises(SyntaxError):
+        XbmImagePlugin.XbmImageFile(b)
+
 
 def test_save_wrong_mode(tmp_path: Path) -> None:
     im = hopper()
diff --git a/src/PIL/XbmImagePlugin.py b/src/PIL/XbmImagePlugin.py
index 69ce54ebf19..e1818fac91c 100644
--- a/src/PIL/XbmImagePlugin.py
+++ b/src/PIL/XbmImagePlugin.py
@@ -80,7 +80,10 @@ def _open(self) -> None:
                 if line.endswith(b"_bits[] = {"):
                     offset = self.fp.tell()
                 break
-            value = int(line.split().pop())
+            try:
+                value = int(line.split().pop())
+            except ValueError:
+                break
             if b"width " in line:
                 width = value
             elif b"height " in line: