diff --git a/lib/xcore.js b/lib/xcore.js
index cf073e4..17eb9ed 100644
--- a/lib/xcore.js
+++ b/lib/xcore.js
@@ -119,6 +119,7 @@ XClient.prototype.init = function(stream)
 
     this.startHandshake();
     this._closing = false;
+    this._unusedIds = [];
 }
 
 // TODO: close() = set 'closing' flag, watch it in replies and writeQueue, terminate if empty
@@ -247,12 +248,17 @@ XClient.prototype.importRequestsFromTemplates = function(target, reqs)
 
 XClient.prototype.AllocID = function()
 {
-    // TODO: handle overflow (XCMiscGetXIDRange from XC_MISC ext)
-    // TODO: unused id buffer
-    this.display.rsrc_id++;
-    return (this.display.rsrc_id << this.display.rsrc_shift) + this.display.resource_base;
-}
+  if (this._unusedIds.length > 0) {
+    return this._unusedIds.pop();
+  }
+  // TODO: handle overflow (XCMiscGetXIDRange from XC_MISC ext)
+  this.display.rsrc_id++;
+  return (this.display.rsrc_id << this.display.rsrc_shift) + this.display.resource_base;
+};
 
+XClient.prototype.ReleaseID = function(id) {
+  this._unusedIds.push(id);
+};
 
 // TODO: move core events unpackers to corereqs.js
 XClient.prototype.unpackEvent = function(type, seq, extra, code, raw, headerBuf)