diff --git a/Lib/test/test_sax.py b/Lib/test/test_sax.py
index af97888..8e279ce 100644
--- a/Lib/test/test_sax.py
+++ b/Lib/test/test_sax.py
@@ -489,6 +489,41 @@
     else:
         return 0
 
+def test_sax_parse_exception_str():
+    # pass various values from a locator to the SAXParseException to
+    # make sure that the __str__() doesn't fall apart when None is
+    # passed instead of an integer line and column number
+    #
+    # use "normal" values for the locator:
+    str(SAXParseException("message", None,
+                          DummyLocator(1, 1)))
+    # use None for the line number:
+    str(SAXParseException("message", None,
+                          DummyLocator(None, 1)))
+    # use None for the column number:
+    str(SAXParseException("message", None,
+                          DummyLocator(1, None)))
+    # use None for both:
+    str(SAXParseException("message", None,
+                          DummyLocator(None, None)))
+    return 1
+
+class DummyLocator:
+    def __init__(self, lineno, colno):
+        self._lineno = lineno
+        self._colno = colno
+
+    def getPublicId(self):
+        return "pubid"
+
+    def getSystemId(self):
+        return "sysid"
+
+    def getLineNumber(self):
+        return self._lineno
+
+    def getColumnNumber(self):
+        return self._colno
 
 # ===========================================================================
 #
diff --git a/Lib/xml/sax/_exceptions.py b/Lib/xml/sax/_exceptions.py
index 7f128f6..628e80d 100644
--- a/Lib/xml/sax/_exceptions.py
+++ b/Lib/xml/sax/_exceptions.py
@@ -91,8 +91,13 @@
         sysid = self.getSystemId()
         if sysid is None:
             sysid = "<unknown>"
-        return "%s:%d:%d: %s" % (sysid, self.getLineNumber(),
-                                 self.getColumnNumber(), self._msg)
+        linenum = self.getLineNumber()
+        if linenum is None:
+           linenum = "?"
+        colnum = self.getColumnNumber()
+        if colnum is None:
+           colnum = "?"
+        return "%s:%s:%s: %s" % (sysid, linenum, colnum, self._msg)
 
 
 # ===== SAXNOTRECOGNIZEDEXCEPTION =====