diff --git a/glib/ghash.c b/glib/ghash.c
index 9fcdcc770..14d0fdad5 100644
--- a/glib/ghash.c
+++ b/glib/ghash.c
@@ -829,8 +829,10 @@ g_hash_table_iter_remove (GHashTableIter *iter)
  * If @key has been taken out of the existing node (ie it is not
  * passed in via a g_hash_table_insert/replace) call, then @reusing_key
  * should be %TRUE.
+ *
+ * Returns: %TRUE if the key did not exist yet
  */
-static void
+static gboolean
 g_hash_table_insert_node (GHashTable *hash_table,
                           guint       node_index,
                           guint       key_hash,
@@ -921,6 +923,8 @@ g_hash_table_insert_node (GHashTable *hash_table,
       if (hash_table->value_destroy_func)
         (* hash_table->value_destroy_func) (value_to_free);
     }
+
+  return !already_exists;
 }
 
 /**
@@ -1138,8 +1142,10 @@ g_hash_table_lookup_extended (GHashTable    *hash_table,
  * Do a lookup of @key. If it is found, replace it with the new
  * @value (and perhaps the new @key). If it is not found, create
  * a new node.
+ *
+ * Returns: %TRUE if the key did not exist yet
  */
-static void
+static gboolean
 g_hash_table_insert_internal (GHashTable *hash_table,
                               gpointer    key,
                               gpointer    value,
@@ -1148,11 +1154,11 @@ g_hash_table_insert_internal (GHashTable *hash_table,
   guint key_hash;
   guint node_index;
 
-  g_return_if_fail (hash_table != NULL);
+  g_return_val_if_fail (hash_table != NULL, FALSE);
 
   node_index = g_hash_table_lookup_node (hash_table, key, &key_hash);
 
-  g_hash_table_insert_node (hash_table, node_index, key_hash, key, value, keep_new_key, FALSE);
+  return g_hash_table_insert_node (hash_table, node_index, key_hash, key, value, keep_new_key, FALSE);
 }
 
 /**
@@ -1169,13 +1175,15 @@ g_hash_table_insert_internal (GHashTable *hash_table,
  * value is freed using that function. If you supplied a
  * @key_destroy_func when creating the #GHashTable, the passed
  * key is freed using that function.
+ *
+ * Returns: %TRUE if the key did not exist yet
  */
-void
+gboolean
 g_hash_table_insert (GHashTable *hash_table,
                      gpointer    key,
                      gpointer    value)
 {
-  g_hash_table_insert_internal (hash_table, key, value, FALSE);
+  return g_hash_table_insert_internal (hash_table, key, value, FALSE);
 }
 
 /**
@@ -1191,13 +1199,15 @@ g_hash_table_insert (GHashTable *hash_table,
  * the #GHashTable, the old value is freed using that function.
  * If you supplied a @key_destroy_func when creating the
  * #GHashTable, the old key is freed using that function.
+ *
+ * Returns: %TRUE of the key did not exist yet
  */
-void
+gboolean
 g_hash_table_replace (GHashTable *hash_table,
                       gpointer    key,
                       gpointer    value)
 {
-  g_hash_table_insert_internal (hash_table, key, value, TRUE);
+  return g_hash_table_insert_internal (hash_table, key, value, TRUE);
 }
 
 /**
@@ -1213,13 +1223,15 @@ g_hash_table_replace (GHashTable *hash_table,
  * corresponding value it is able to be stored more efficiently.  See
  * the discussion in the section description.
  *
+ * Returns: %TRUE if the key did not exist yet
+ *
  * Since: 2.32
- **/
-void
+ */
+gboolean
 g_hash_table_add (GHashTable *hash_table,
                   gpointer    key)
 {
-  g_hash_table_insert_internal (hash_table, key, key, TRUE);
+  return g_hash_table_insert_internal (hash_table, key, key, TRUE);
 }
 
 /**
diff --git a/glib/ghash.h b/glib/ghash.h
index 796f74417..125307626 100644
--- a/glib/ghash.h
+++ b/glib/ghash.h
@@ -66,15 +66,15 @@ GHashTable* g_hash_table_new_full          (GHashFunc       hash_func,
 GLIB_AVAILABLE_IN_ALL
 void        g_hash_table_destroy           (GHashTable     *hash_table);
 GLIB_AVAILABLE_IN_ALL
-void        g_hash_table_insert            (GHashTable     *hash_table,
+gboolean    g_hash_table_insert            (GHashTable     *hash_table,
                                             gpointer        key,
                                             gpointer        value);
 GLIB_AVAILABLE_IN_ALL
-void        g_hash_table_replace           (GHashTable     *hash_table,
+gboolean    g_hash_table_replace           (GHashTable     *hash_table,
                                             gpointer        key,
                                             gpointer        value);
 GLIB_AVAILABLE_IN_ALL
-void        g_hash_table_add               (GHashTable     *hash_table,
+gboolean    g_hash_table_add               (GHashTable     *hash_table,
                                             gpointer        key);
 GLIB_AVAILABLE_IN_ALL
 gboolean    g_hash_table_remove            (GHashTable     *hash_table,
diff --git a/glib/tests/hash.c b/glib/tests/hash.c
index e03ebfe62..e882227c0 100644
--- a/glib/tests/hash.c
+++ b/glib/tests/hash.c
@@ -508,9 +508,11 @@ set_hash_test (void)
   for (i = 2; i < 5000; i += 7)
     {
       char *s = g_strdup_printf ("%d", i);
-      g_hash_table_add (hash_table, s);
+      g_assert (g_hash_table_add (hash_table, s));
     }
 
+  g_assert (!g_hash_table_add (hash_table, g_strdup_printf ("%d", 2)));
+
   i = 0;
   g_hash_table_foreach (hash_table, set_check, &i);
   g_assert_cmpint (i, ==, g_hash_table_size (hash_table));
@@ -520,7 +522,11 @@ set_hash_test (void)
   g_assert (!g_hash_table_contains (hash_table, "a"));
 
   /* this will cause the hash table to loose set nature */
-  g_hash_table_insert (hash_table, g_strdup ("a"), "b");
+  g_assert (g_hash_table_insert (hash_table, g_strdup ("a"), "b"));
+  g_assert (!g_hash_table_insert (hash_table, g_strdup ("a"), "b"));
+
+  g_assert (g_hash_table_replace (hash_table, g_strdup ("c"), "d"));
+  g_assert (!g_hash_table_replace (hash_table, g_strdup ("c"), "d"));
 
   g_assert_cmpstr (g_hash_table_lookup (hash_table, "2"), ==, "2");
   g_assert_cmpstr (g_hash_table_lookup (hash_table, "a"), ==, "b");