diff --git a/src/hb-map.hh b/src/hb-map.hh
index c62b9d7bb..9b435c7d7 100644
--- a/src/hb-map.hh
+++ b/src/hb-map.hh
@@ -35,8 +35,7 @@
  */
 
 template <typename K, typename V,
-	  typename v_invalid_t = V,
-	  v_invalid_t vINVALID = std::is_pointer<V>::value ? 0 : std::is_signed<V>::value ? hb_int_min (V) : (V) -1>
+	  bool minus_one = false>
 struct hb_hashmap_t
 {
   hb_hashmap_t ()  { init (); }
@@ -71,19 +70,24 @@ struct hb_hashmap_t
     uint32_t is_tombstone_ : 1;
     V value;
 
-
-
     bool is_used () const { return is_used_; }
     void set_used (bool is_used) { is_used_ = is_used; }
     bool is_tombstone () const { return is_tombstone_; }
     void set_tombstone (bool is_tombstone) { is_tombstone_ = is_tombstone; }
     bool is_real () const { return is_used_ && !is_tombstone_; }
 
+    template <bool v = minus_one,
+	      hb_enable_if (v == false)>
+    static V default_value () { return V(); };
+    template <bool v = minus_one,
+	      hb_enable_if (v == true)>
+    static V default_value () { return V(-1); };
+
     void clear ()
     {
       new (std::addressof (key)) K ();
       new (std::addressof (value)) V ();
-      value = hb_coerce<V> (vINVALID);
+      value = default_value ();
       hash = 0;
       is_used_ = false;
       is_tombstone_ = false;
@@ -200,12 +204,12 @@ struct hb_hashmap_t
 
   V get (K key) const
   {
-    if (unlikely (!items)) return hb_coerce<V> (vINVALID);
+    if (unlikely (!items)) return item_t::default_value ();
     unsigned int i = bucket_for (key);
-    return items[i].is_real () && items[i] == key ? items[i].value : hb_coerce<V> (vINVALID);
+    return items[i].is_real () && items[i] == key ? items[i].value : item_t::default_value ();
   }
 
-  void del (K key) { set_with_hash (key, hb_hash (key), hb_coerce<V> (vINVALID), true); }
+  void del (K key) { set_with_hash (key, hb_hash (key), item_t::default_value (), true); }
 
   /* Has interface. */
   typedef V value_t;
@@ -214,8 +218,7 @@ struct hb_hashmap_t
   {
     const V &v = (*this)[k];
     if (vp) *vp = v;
-    const V vinv = hb_coerce<V> (vINVALID);
-    return v != vinv;
+    return v != item_t::default_value (); // TODO
   }
   /* Projection. */
   V operator () (K k) const { return get (k); }
@@ -398,13 +401,11 @@ struct hb_hashmap_t
 
 struct hb_map_t : hb_hashmap_t<hb_codepoint_t,
 			       hb_codepoint_t,
-			       hb_codepoint_t,
-			       HB_MAP_VALUE_INVALID>
+			       true>
 {
   using hashmap = hb_hashmap_t<hb_codepoint_t,
 			       hb_codepoint_t,
-			       hb_codepoint_t,
-			       HB_MAP_VALUE_INVALID>;
+			       true>;
 
   ~hb_map_t () = default;
   hb_map_t () : hashmap () {}
diff --git a/src/hb-ot-post-table-v2subset.hh b/src/hb-ot-post-table-v2subset.hh
index 8c0312fa4..718b09d7e 100644
--- a/src/hb-ot-post-table-v2subset.hh
+++ b/src/hb-ot-post-table-v2subset.hh
@@ -78,7 +78,7 @@ HB_INTERNAL bool postV2Tail::subset (hb_subset_context_t *c) const
 
   post::accelerator_t _post (c->plan->source);
 
-  hb_hashmap_t<hb_bytes_t, unsigned> glyph_name_to_new_index;
+  hb_hashmap_t<hb_bytes_t, unsigned, true> glyph_name_to_new_index;
   for (hb_codepoint_t new_gid = 0; new_gid < num_glyphs; new_gid++)
   {
     hb_codepoint_t old_gid = reverse_glyph_map.get (new_gid);
diff --git a/src/hb-serialize.hh b/src/hb-serialize.hh
index 3f4535ce4..6f56faafe 100644
--- a/src/hb-serialize.hh
+++ b/src/hb-serialize.hh
@@ -719,8 +719,7 @@ struct hb_serialize_context_t
   hb_vector_t<object_t *> packed;
 
   /* Map view of packed objects. */
-  hb_hashmap_t<const object_t *, objidx_t,
-	       objidx_t, 0> packed_map;
+  hb_hashmap_t<const object_t *, objidx_t> packed_map;
 };
 
 #endif /* HB_SERIALIZE_HH */
diff --git a/src/test-map.cc b/src/test-map.cc
index e62f65091..0351d8161 100644
--- a/src/test-map.cc
+++ b/src/test-map.cc
@@ -27,11 +27,6 @@
 #include "hb-set.hh"
 #include <string>
 
-static const std::string invalid{"invalid"};
-static const hb_map_t invalid_map{};
-static const hb_set_t invalid_set{};
-static const hb_vector_t<unsigned> invalid_vector{};
-
 int
 main (int argc, char **argv)
 {
@@ -127,19 +122,19 @@ main (int argc, char **argv)
 
   /* Test class key / value types. */
   {
-    hb_hashmap_t<hb_bytes_t, int, int, 0> m1;
-    hb_hashmap_t<int, hb_bytes_t, std::nullptr_t, nullptr> m2;
-    hb_hashmap_t<hb_bytes_t, hb_bytes_t, std::nullptr_t, nullptr> m3;
+    hb_hashmap_t<hb_bytes_t, int> m1;
+    hb_hashmap_t<int, hb_bytes_t> m2;
+    hb_hashmap_t<hb_bytes_t, hb_bytes_t> m3;
     assert (m1.get_population () == 0);
     assert (m2.get_population () == 0);
     assert (m3.get_population () == 0);
   }
 
   {
-    hb_hashmap_t<int, int, int, 0> m0;
-    hb_hashmap_t<std::string, int, int, 0> m1;
-    hb_hashmap_t<int, std::string, const std::string*, &invalid> m2;
-    hb_hashmap_t<std::string, std::string, const std::string*, &invalid> m3;
+    hb_hashmap_t<int, int> m0;
+    hb_hashmap_t<std::string, int> m1;
+    hb_hashmap_t<int, std::string> m2;
+    hb_hashmap_t<std::string, std::string> m3;
 
     std::string s;
     for (unsigned i = 1; i < 1000; i++)
@@ -156,67 +151,49 @@ main (int argc, char **argv)
   {
     using pair = hb_pair_t<hb_codepoint_t, hb_codepoint_t>;
 
-    hb_hashmap_t<hb_map_t, hb_map_t, const hb_map_t *, &invalid_map> m1;
-    hb_hashmap_t<hb_map_t, hb_map_t, std::nullptr_t, nullptr> m2;
+    hb_hashmap_t<hb_map_t, hb_map_t> m1;
 
     m1.set (hb_map_t (), hb_map_t {});
-    m2.set (hb_map_t (), hb_map_t {});
 
     m1.set (hb_map_t (), hb_map_t {pair (1u, 2u)});
-    m2.set (hb_map_t (), hb_map_t {pair (1u, 2u)});
 
     m1.set (hb_map_t {pair (1u, 2u)}, hb_map_t {pair (2u, 3u)});
-    m2.set (hb_map_t {pair (1u, 2u)}, hb_map_t {pair (2u, 3u)});
 
     assert (m1.get (hb_map_t ()) == hb_map_t {pair (1u, 2u)});
-    assert (m2.get (hb_map_t ()) == hb_map_t {pair (1u, 2u)});
 
     assert (m1.get (hb_map_t {pair (1u, 2u)}) == hb_map_t {pair (2u, 3u)});
-    assert (m2.get (hb_map_t {pair (1u, 2u)}) == hb_map_t {pair (2u, 3u)});
   }
 
   /* Test hashing sets. */
   {
-    hb_hashmap_t<hb_set_t, hb_set_t, const hb_set_t *, &invalid_set> m1;
-    hb_hashmap_t<hb_set_t, hb_set_t, std::nullptr_t, nullptr> m2;
+    hb_hashmap_t<hb_set_t, hb_set_t> m1;
 
     m1.set (hb_set_t (), hb_set_t ());
-    m2.set (hb_set_t (), hb_set_t ());
 
     m1.set (hb_set_t (), hb_set_t {1});
-    m2.set (hb_set_t (), hb_set_t {1});
 
     m1.set (hb_set_t {1, 1000}, hb_set_t {2});
-    m2.set (hb_set_t {1, 1000}, hb_set_t {2});
 
     assert (m1.get (hb_set_t ()) == hb_set_t {1});
-    assert (m2.get (hb_set_t ()) == hb_set_t {1});
 
     assert (m1.get (hb_set_t {1000, 1}) == hb_set_t {2});
-    assert (m2.get (hb_set_t {1000, 1}) == hb_set_t {2});
   }
 
   /* Test hashing vectors. */
   {
     using vector_t = hb_vector_t<unsigned>;
 
-    hb_hashmap_t<vector_t, vector_t, const vector_t *, &invalid_vector> m1;
-    hb_hashmap_t<vector_t, vector_t, std::nullptr_t, nullptr> m2;
+    hb_hashmap_t<vector_t, vector_t> m1;
 
     m1.set (vector_t (), vector_t ());
-    m2.set (vector_t (), vector_t ());
 
     m1.set (vector_t (), vector_t {1});
-    m2.set (vector_t (), vector_t {1});
 
     m1.set (vector_t {1}, vector_t {2});
-    m2.set (vector_t {1}, vector_t {2});
 
     assert (m1.get (vector_t ()) == vector_t {1});
-    assert (m2.get (vector_t ()) == vector_t {1});
 
     assert (m1.get (vector_t {1}) == vector_t {2});
-    assert (m2.get (vector_t {1}) == vector_t {2});
   }
 
   /* Test hb::shared_ptr. */