diff --git a/libs/freetdm/src/ftmod/ftmod_sangoma_isdn/ftmod_sangoma_isdn.2008.vcproj b/libs/freetdm/src/ftmod/ftmod_sangoma_isdn/ftmod_sangoma_isdn.2008.vcproj
index 2e7fb82041..01395cb1db 100644
--- a/libs/freetdm/src/ftmod/ftmod_sangoma_isdn/ftmod_sangoma_isdn.2008.vcproj
+++ b/libs/freetdm/src/ftmod/ftmod_sangoma_isdn/ftmod_sangoma_isdn.2008.vcproj
@@ -118,7 +118,7 @@
 			<Tool
 				Name="VCCLCompilerTool"
 				AdditionalIncludeDirectories="&quot;C:\Program Files\sangoma\sng_isdn\include&quot;;../../include;&quot;C:\Program Files\Sangoma\include&quot;"
-				PreprocessorDefinitions="WIN32;_DEBUG;_CONSOLE;"
+				PreprocessorDefinitions="WIN32;NDEBUG;_WINDOWS;_USRDLL"
 				MinimalRebuild="true"
 				BasicRuntimeChecks="3"
 				RuntimeLibrary="2"
diff --git a/libs/freetdm/src/ftmod/ftmod_sangoma_isdn/ftmod_sangoma_isdn.2010.vcxproj b/libs/freetdm/src/ftmod/ftmod_sangoma_isdn/ftmod_sangoma_isdn.2010.vcxproj
index 6339fe9912..d7b75d8df4 100644
--- a/libs/freetdm/src/ftmod/ftmod_sangoma_isdn/ftmod_sangoma_isdn.2010.vcxproj
+++ b/libs/freetdm/src/ftmod/ftmod_sangoma_isdn/ftmod_sangoma_isdn.2010.vcxproj
@@ -134,7 +134,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
     <ClCompile>
-      <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <MinimalRebuild>true</MinimalRebuild>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
       <RuntimeLibrary>MultiThreadedDLL</RuntimeLibrary>
@@ -157,7 +157,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'">
     <ClCompile>
-      <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
       <RuntimeLibrary>MultiThreadedDLL</RuntimeLibrary>
       <PrecompiledHeader>