diff --git a/src/common/datetimefmt.cpp b/src/common/datetimefmt.cpp
index fed909fe8a..c75d2e2c18 100644
--- a/src/common/datetimefmt.cpp
+++ b/src/common/datetimefmt.cpp
@@ -1408,6 +1408,11 @@ wxDateTime::ParseFormat(const wxString& date,
 
             case wxT('z'):
                 {
+                    // check that we have something here at all
+                    if ( input == end )
+                        return false;
+
+                    // and then check that it's either plus or minus sign
                     bool minusFound;
                     if ( *input == wxT('-') )
                         minusFound = true;
diff --git a/tests/datetime/datetimetest.cpp b/tests/datetime/datetimetest.cpp
index 3d4fad74d1..71821d92e8 100644
--- a/tests/datetime/datetimetest.cpp
+++ b/tests/datetime/datetimetest.cpp
@@ -829,6 +829,9 @@ void DateTimeTestCase::TestTimeFormat()
     CPPUNIT_ASSERT( dt.ParseFormat("17", "%d") );
     CPPUNIT_ASSERT_EQUAL( 17, dt.GetDay() );
 
+    // test some degenerate cases
+    CPPUNIT_ASSERT( !dt.ParseFormat("", "%z") );
+
     // test compilation of some calls which should compile (and not result in
     // ambiguity because of char*<->wxCStrData<->wxString conversions)
     wxString s("foo");