diff --git a/lib/jasmine-0.11.0.js b/lib/jasmine-0.11.0.js
index 65c5a104..8c7833d4 100644
--- a/lib/jasmine-0.11.0.js
+++ b/lib/jasmine-0.11.0.js
@@ -409,6 +409,11 @@ jasmine.createSpyObj = function(baseName, methodNames) {
   return obj;
 };
 
+/**
+ * All parameters are pretty-printed and concatenated together, then written to the current spec's output.
+ *
+ * Be careful not to leave calls to <code>jasmine.log</code> in production code.
+ */
 jasmine.log = function() {
   var spec = jasmine.getEnv().currentSpec;
   spec.log.apply(spec, arguments);
@@ -1817,6 +1822,11 @@ jasmine.Spec.prototype.results = function() {
   return this.results_;
 };
 
+/**
+ * All parameters are pretty-printed and concatenated together, then written to the spec's output.
+ *
+ * Be careful not to leave calls to <code>jasmine.log</code> in production code.
+ */
 jasmine.Spec.prototype.log = function() {
   return this.results_.log(arguments);
 };
@@ -2180,9 +2190,9 @@ jasmine.FakeTimer.prototype.runFunctionsWithinRange = function(oldMillis, nowMil
         funcToRun.funcToCall();
         if (funcToRun.recurring) {
           this.scheduleFunction(funcToRun.timeoutKey,
-            funcToRun.funcToCall,
-            funcToRun.millis,
-            true);
+              funcToRun.funcToCall,
+              funcToRun.millis,
+              true);
         }
       } catch(e) {
       }
@@ -2226,10 +2236,12 @@ jasmine.Clock = {
   },
 
   useMock: function() {
-    var spec = jasmine.getEnv().currentSpec;
-    spec.after(jasmine.Clock.uninstallMock);
+    if (!jasmine.Clock.isInstalled()) {
+      var spec = jasmine.getEnv().currentSpec;
+      spec.after(jasmine.Clock.uninstallMock);
 
-    jasmine.Clock.installMock();
+      jasmine.Clock.installMock();
+    }
   },
 
   installMock: function() {
@@ -2237,6 +2249,7 @@ jasmine.Clock = {
   },
 
   uninstallMock: function() {
+    jasmine.log("uninstall")
     jasmine.Clock.assertInstalled();
     jasmine.Clock.installed = jasmine.Clock.real;
   },
@@ -2249,11 +2262,15 @@ jasmine.Clock = {
   },
 
   assertInstalled: function() {
-    if (jasmine.Clock.installed != jasmine.Clock.defaultFakeTimer) {
+    if (!jasmine.Clock.isInstalled()) {
       throw new Error("Mock clock is not installed, use jasmine.Clock.useMock()");
     }
   },
 
+  isInstalled: function() {
+    return jasmine.Clock.installed == jasmine.Clock.defaultFakeTimer;
+  },
+
   installed: null
 };
 jasmine.Clock.installed = jasmine.Clock.real;
@@ -2287,7 +2304,7 @@ jasmine.getGlobal().clearInterval = function(timeoutKey) {
   if (jasmine.Clock.installed.clearTimeout.apply) {
     return jasmine.Clock.installed.clearInterval.apply(this, arguments);
   } else {
-  return jasmine.Clock.installed.clearInterval(timeoutKey);
+    return jasmine.Clock.installed.clearInterval(timeoutKey);
   }
 };
 
@@ -2296,5 +2313,5 @@ jasmine.version_= {
   "major": 0,
   "minor": 11,
   "build": 0,
-  "revision": 1277253997
+  "revision": 1277316068
   };
diff --git a/spec/runner.html b/spec/runner.html
index ed47b96e..6ebd7523 100644
--- a/spec/runner.html
+++ b/spec/runner.html
@@ -39,6 +39,7 @@
   <script type="text/javascript" src="suites/ExceptionsSpec.js"></script>
   <script type="text/javascript" src="suites/JsApiReporterSpec.js"></script>
   <script type="text/javascript" src="suites/MatchersSpec.js"></script>
+  <script type="text/javascript" src="suites/MockClockSpec.js"></script>
   <script type="text/javascript" src="suites/MultiReporterSpec.js"></script>
   <script type="text/javascript" src="suites/NestedResultsSpec.js"></script>
   <script type="text/javascript" src="suites/PrettyPrintSpec.js"></script>
diff --git a/spec/suites/MockClockSpec.js b/spec/suites/MockClockSpec.js
index dca3ff2f..be683440 100644
--- a/spec/suites/MockClockSpec.js
+++ b/spec/suites/MockClockSpec.js
@@ -31,4 +31,8 @@ describe("MockClock", function () {
       expect(interval).toEqual(2);
     });
   });
+
+  it("shouldn't complain if you call jasmine.Clock.useMock() more than once", function() {
+    jasmine.Clock.useMock();
+  });
 });
diff --git a/src/mock-timeout.js b/src/mock-timeout.js
index 136d0243..c03f9f63 100755
--- a/src/mock-timeout.js
+++ b/src/mock-timeout.js
@@ -64,9 +64,9 @@ jasmine.FakeTimer.prototype.runFunctionsWithinRange = function(oldMillis, nowMil
         funcToRun.funcToCall();
         if (funcToRun.recurring) {
           this.scheduleFunction(funcToRun.timeoutKey,
-            funcToRun.funcToCall,
-            funcToRun.millis,
-            true);
+              funcToRun.funcToCall,
+              funcToRun.millis,
+              true);
         }
       } catch(e) {
       }
@@ -110,10 +110,12 @@ jasmine.Clock = {
   },
 
   useMock: function() {
-    var spec = jasmine.getEnv().currentSpec;
-    spec.after(jasmine.Clock.uninstallMock);
+    if (!jasmine.Clock.isInstalled()) {
+      var spec = jasmine.getEnv().currentSpec;
+      spec.after(jasmine.Clock.uninstallMock);
 
-    jasmine.Clock.installMock();
+      jasmine.Clock.installMock();
+    }
   },
 
   installMock: function() {
@@ -121,6 +123,7 @@ jasmine.Clock = {
   },
 
   uninstallMock: function() {
+    jasmine.log("uninstall")
     jasmine.Clock.assertInstalled();
     jasmine.Clock.installed = jasmine.Clock.real;
   },
@@ -133,11 +136,15 @@ jasmine.Clock = {
   },
 
   assertInstalled: function() {
-    if (jasmine.Clock.installed != jasmine.Clock.defaultFakeTimer) {
+    if (!jasmine.Clock.isInstalled()) {
       throw new Error("Mock clock is not installed, use jasmine.Clock.useMock()");
     }
   },
 
+  isInstalled: function() {
+    return jasmine.Clock.installed == jasmine.Clock.defaultFakeTimer;
+  },
+
   installed: null
 };
 jasmine.Clock.installed = jasmine.Clock.real;
@@ -171,7 +178,7 @@ jasmine.getGlobal().clearInterval = function(timeoutKey) {
   if (jasmine.Clock.installed.clearTimeout.apply) {
     return jasmine.Clock.installed.clearInterval.apply(this, arguments);
   } else {
-  return jasmine.Clock.installed.clearInterval(timeoutKey);
+    return jasmine.Clock.installed.clearInterval(timeoutKey);
   }
 };