A hotfix is available that improves the SpeechSynthesizer class in the .NET Framework 4.0


A hotfix is available that improves the System.Speech.Synthesis.SpeechSynthesizer class in the Microsoft .NET Framework 4.0. After you install this hotfix, the application can use the SpeechSynthesizer class to read object tokens in the registry. The object tokens in the registry follow the standards that are defined by Microsoft Speech API (SAPI). Therefore, the application can use the SpeechSynthesizer class to load SAPI-compliant text-to-speech (TTS) engines. This includes some third-party TTS engines. 

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Hotfix information

A supported hotfix is now available from Microsoft. However, it is intended to correct only the problem that is described in this article. Apply it only to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

To resolve this problem immediately, contact Microsoft Customer Support Services to obtain the hotfix. For a complete list of Microsoft Customer Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.


To apply this hotfix, you must have the .NET Framework 4.0 installed.

Restart requirement

You do not have to restart the computer after you apply the hotfix if the affected files are not being used.

Hotfix replacement information

This hotfix does not replace any hotfix. 

File Information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

For all supported x86-based versions of Windows XP, of Windows Server 2003, of Windows Vista, of Windows Server 2008, and of Windows 7
File nameFile versionFile sizeDateTimePlatform
For all supported x64-based versions of Windows XP, of Windows Server 2003, of Windows Vista, of Windows Server 2008, of Windows 7, and of Windows Server 2008 R2
File nameFile versionFile sizeDateTimePlatform

More Information

For more information about the Speech API (SAPI) 5.3, visit the following MSDN website:
For more information about the SpeechSynthesizer class, visit the following MSDN website:
For more information about object tokens and registry settings for Speech API 5.3, visit the following MSDN website: