diff --git a/src/lang/periodical_executer.js b/src/lang/periodical_executer.js
index e521bbf..c423262 100644
--- a/src/lang/periodical_executer.js
+++ b/src/lang/periodical_executer.js
@@ -49,20 +49,18 @@ var PeriodicalExecuter = Class.create({
 
   onTimerEvent: function() {
     if (!this.currentlyExecuting) {
-      if (!this.currentlyExecuting) {
-        // IE doesn't support `finally` statements unless all errors are caught.
-        // We mimic the behaviour of `finally` statements by duplicating code
-        // that would belong in it. First at the bottom of the `try` statement
-        // (for errorless cases). Secondly, inside a `catch` statement which
-        // rethrows any caught errors.
-        try {
-          this.currentlyExecuting = true;
-          this.execute();
-          this.currentlyExecuting = false;
-        } catch(e) {
-          this.currentlyExecuting = false;
-          throw e;
-        }
+      // IE doesn't support `finally` statements unless all errors are caught.
+      // We mimic the behaviour of `finally` statements by duplicating code
+      // that would belong in it. First at the bottom of the `try` statement
+      // (for errorless cases). Secondly, inside a `catch` statement which
+      // rethrows any caught errors.
+      try {
+        this.currentlyExecuting = true;
+        this.execute();
+        this.currentlyExecuting = false;
+      } catch(e) {
+        this.currentlyExecuting = false;
+        throw e;
       }
     }
   }
diff --git a/test/unit/periodical_executer_test.js b/test/unit/periodical_executer_test.js
index 9640b33..4fa1909 100644
--- a/test/unit/periodical_executer_test.js
+++ b/test/unit/periodical_executer_test.js
@@ -11,5 +11,25 @@ new Test.Unit.Runner({
     this.wait(600, function() {
       this.assertEqual(3, peEventCount);
     });
+  },
+
+  testOnTimerEventMethod: function() {
+    var testcase = this,
+        pe = {
+          onTimerEvent: PeriodicalExecuter.prototype.onTimerEvent,
+          execute: function() {
+            testcase.assert(pe.currentlyExecuting);
+          }
+        };
+
+    pe.onTimerEvent();
+    this.assert(!pe.currentlyExecuting);
+
+    pe.execute = function() {
+      testcase.assert(pe.currentlyExecuting);
+      throw new Error()
+    }
+    this.assertRaise('Error', pe.onTimerEvent.bind(pe));
+    this.assert(!pe.currentlyExecuting);
   }
 });
\ No newline at end of file