diff --git a/src/gen/lib/grampstype.py b/src/gen/lib/grampstype.py
index c43ec2301..1ece5739f 100644
--- a/src/gen/lib/grampstype.py
+++ b/src/gen/lib/grampstype.py
@@ -82,8 +82,13 @@ class GrampsType(object):
             self.string = u''
 
     def __set_tuple(self, value):
-        self.val = value[0]
-        self.string = value[1]
+        v,s = self._DEFAULT,u''
+        if len(value) > 0:
+            v = value[0]
+            if len(value) > 1:
+                s = value[1]
+        self.val = v
+        self.string = s
 
     def __set_int(self, value):
         self.val = value
diff --git a/src/gen/lib/test/grampstype_test.py b/src/gen/lib/test/grampstype_test.py
new file mode 100644
index 000000000..2b07c2f35
--- /dev/null
+++ b/src/gen/lib/test/grampstype_test.py
@@ -0,0 +1,56 @@
+""" unittest for grampstype """
+
+import unittest as U
+
+from test.test_util import msg
+from gen.lib.grampstype import GrampsType, _init_map
+
+# some simple map items to test with
+vals = "zz ab cd ef".split()
+keys = range(len(vals))
+MAP = [ (k,v*2,v) for (k,v) in zip(keys, vals) ]
+
+class GT0(GrampsType):
+    _DEFAULT  = 1 # just avoiding the pre-coded 0
+    _CUSTOM   = 3 # just avoiding the pre-coded 0
+    _DATAMAP = MAP
+
+class Test1(U.TestCase):
+
+    # some basic tests
+    def test1a(s):
+        s.gt=GT0()
+        s.assertTrue(isinstance(s.gt, GrampsType))
+        # spot-check that MAPs get built
+        e= len(keys)
+        g= len(s.gt._E2IMAP)
+        s.assertEquals(g,e, msg(g,e, "expected length of E2IMAP"))
+
+    # init sets values for int, str, tuple 
+    # (we ignore instance here -- maybe SB tested, too?)
+    # this test depends on having _DEFAULT=1, _CUSTOM=3
+    # NB: tuple tests w/ lengths < 2 fail before release 10403
+    def test1b(s):
+        for i,v,u in ( 
+                (None, 1,u''),      # all DEFAULT
+                (0, 0,u''), 
+                (1, 1,u''), 
+                ('efef', 3,'efef'), # matches CUSTOM
+                ('zzzz', 0,u''),
+                (u'x',   3,u'x'),   # nomatch gives CUSTOM   
+                ('',     3,''),     # nomatch gives CUSTOM   
+                ((0,'zero'), 0,'zero'), # normal behavior
+                ((2,),       2,u''),    # DEFAULT-string, just like int 
+                ((),         1,u''),    # DEFAULT-pair      
+                ):
+            s.gt = GT0(i)
+            g= s.gt.val
+            s.assertEquals(g,v, 
+                msg(g,v, "initialization val from '%s'" % `i`))
+            g= s.gt.string
+            s.assertEquals(g,u, 
+                msg(g,u, "initialization string from '%s'" % `i`))
+
+if __name__ == "__main__":
+    U.main()
+