diff --git a/xlsxwriter/test/workbook/test_check_sheetname.py b/xlsxwriter/test/workbook/test_check_sheetname.py
index 25a54bf16..62e84f670 100644
--- a/xlsxwriter/test/workbook/test_check_sheetname.py
+++ b/xlsxwriter/test/workbook/test_check_sheetname.py
@@ -40,6 +40,12 @@ def test_check_sheetname(self):
         exp = "Sheet4"
         self.assertEqual(got, exp)
 
+    def test_check_sheetname_with_incorrect_dtype(self):
+        """Test the _check_sheetname() method with exception"""
+
+        name = 42
+        self.assertRaises(TypeError, self.workbook._check_sheetname, name)
+
     def test_check_sheetname_with_long_name(self):
         """Test the _check_sheetname() method with exception"""
 
diff --git a/xlsxwriter/workbook.py b/xlsxwriter/workbook.py
index c0994a7d0..708ffbddf 100644
--- a/xlsxwriter/workbook.py
+++ b/xlsxwriter/workbook.py
@@ -841,6 +841,11 @@ def _check_sheetname(self, sheetname, is_chartsheet=False):
             else:
                 sheetname = self.sheet_name + str(self.sheetname_count)
 
+        if not isinstance(sheetname, str):
+            raise TypeError(
+                "The sheet name must be of type str, is type %s." % type(sheetname)
+            )
+
         # Check that sheet sheetname is <= 31. Excel limit.
         if len(sheetname) > 31:
             raise InvalidWorksheetName(