diff --git a/develop/untests.lua b/develop/untests.lua
index 582b9c7..8238dec 100644
--- a/develop/untests.lua
+++ b/develop/untests.lua
@@ -4,15 +4,10 @@ local evo = require 'evolved'
 
 evo.debug_mode(true)
 
-do
-    local e1, e2 = evo.id(), evo.id()
-    assert(e1 ~= e2)
-end
-
 do
     local i = evo.id()
 
-    for _ = 1, 0xFFE do
+    for _ = 1, 0xFFFFE do
         local _, v0 = evo.unpack(i)
         evo.destroy(i)
         i = evo.id()
@@ -22,7 +17,7 @@ do
 
     do
         local _, v = evo.unpack(i)
-        assert(v == 0xFFF)
+        assert(v == 0xFFFFF)
     end
 
     evo.destroy(i)
@@ -34,6 +29,31 @@ do
     end
 end
 
+do
+    local e1, e2 = evo.id(), evo.id()
+    assert(e1 ~= e2)
+
+    assert(evo.is_alive(e1))
+    assert(evo.is_alive(e2))
+
+    assert(evo.destroy(e1))
+
+    assert(not evo.is_alive(e1))
+    assert(evo.is_alive(e2))
+
+    assert(evo.destroy(e1))
+    assert(evo.destroy(e2))
+
+    assert(not evo.is_alive(e1))
+    assert(not evo.is_alive(e2))
+
+    assert(evo.destroy(e1))
+    assert(evo.destroy(e2))
+
+    assert(not evo.is_alive(e1))
+    assert(not evo.is_alive(e2))
+end
+
 do
     do
         local i0 = evo.id(0)
@@ -5076,9 +5096,15 @@ do
 end
 
 do
-    local id = evo.pack(0xFFFFF, 0xFFF)
+    local id = evo.pack(0xBCDEF, 0xFEDCB)
     local index, version = evo.unpack(id)
-    assert(index == 0xFFFFF and version == 0xFFF)
+    assert(index == 0xBCDEF and version == 0xFEDCB)
+end
+
+do
+    local id = evo.pack(0xFFFFF, 0xFFFFF)
+    local index, version = evo.unpack(id)
+    assert(index == 0xFFFFF and version == 0xFFFFF)
 end
 
 do
diff --git a/evolved.lua b/evolved.lua
index ca7f7f3..d5f56ef 100644
--- a/evolved.lua
+++ b/evolved.lua
@@ -269,7 +269,7 @@ local function __release_id(id)
         __error_fmt('id is not acquired or already released')
     end
 
-    shifted_version = shifted_version == 0xFFF00000
+    shifted_version = shifted_version == 0xFFFFF00000
         and 0x100000
         or shifted_version + 0x100000
 
@@ -4621,8 +4621,8 @@ __evolved_pack = function(index, version)
         __error_fmt('id index out of range [1;0xFFFFF]')
     end
 
-    if version < 1 or version > 0xFFF then
-        __error_fmt('id version out of range [1;0xFFF]')
+    if version < 1 or version > 0xFFFFF then
+        __error_fmt('id version out of range [1;0xFFFFF]')
     end
 
     local shifted_version = version * 0x100000
@@ -7989,4 +7989,6 @@ evolved.query = __evolved_query
 evolved.phase = __evolved_phase
 evolved.system = __evolved_system
 
+evolved.collect_garbage()
+
 return evolved