diff --git a/lib/jasmine-core/jasmine.js b/lib/jasmine-core/jasmine.js
index 401d5df6..ee776eab 100644
--- a/lib/jasmine-core/jasmine.js
+++ b/lib/jasmine-core/jasmine.js
@@ -7054,10 +7054,9 @@ getJasmineRequireObj().MockDate = function(j$) {
         currentTime = mockDate.getTime();
       } else {
         if (!j$.util.isUndefined(mockDate)) {
-          j$.getEnv().deprecated(
+          throw new Error(
             'The argument to jasmine.clock().mockDate(), if specified, ' +
-              'should be a Date instance. Passing anything other than a Date ' +
-              'will be treated as an error in a future release.'
+              'should be a Date instance.'
           );
         }
 
diff --git a/spec/core/ClockSpec.js b/spec/core/ClockSpec.js
index 126fe8ca..69c05fc4 100644
--- a/spec/core/ClockSpec.js
+++ b/spec/core/ClockSpec.js
@@ -950,7 +950,7 @@ describe('Clock (acceptance)', function() {
     expect(timeoutDate).toEqual(baseTime.getTime() + 150);
   });
 
-  it('logs a deprecation when mockDate is called with a non-Date', function() {
+  it('throws mockDate is called with a non-Date', function() {
     var delayedFunctionScheduler = new jasmineUnderTest.DelayedFunctionScheduler(),
       global = { Date: Date },
       mockDate = new jasmineUnderTest.MockDate(global),
@@ -963,12 +963,9 @@ describe('Clock (acceptance)', function() {
       ),
       env = jasmineUnderTest.getEnv();
 
-    spyOn(env, 'deprecated');
-    clock.mockDate(12345);
-    expect(env.deprecated).toHaveBeenCalledWith(
+    expect(() => clock.mockDate(12345)).toThrowError(
       'The argument to jasmine.clock().mockDate(), if specified, should be ' +
-        'a Date instance. Passing anything other than a Date will be ' +
-        'treated as an error in a future release.'
+        'a Date instance.'
     );
   });
 
diff --git a/src/core/MockDate.js b/src/core/MockDate.js
index e8738a44..feefe458 100644
--- a/src/core/MockDate.js
+++ b/src/core/MockDate.js
@@ -17,10 +17,9 @@ getJasmineRequireObj().MockDate = function(j$) {
         currentTime = mockDate.getTime();
       } else {
         if (!j$.util.isUndefined(mockDate)) {
-          j$.getEnv().deprecated(
+          throw new Error(
             'The argument to jasmine.clock().mockDate(), if specified, ' +
-              'should be a Date instance. Passing anything other than a Date ' +
-              'will be treated as an error in a future release.'
+              'should be a Date instance.'
           );
         }