diff --git a/PCbuild/tcl.vcxproj b/PCbuild/tcl.vcxproj
--- a/PCbuild/tcl.vcxproj
+++ b/PCbuild/tcl.vcxproj
@@ -61,7 +61,8 @@
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   
   <PropertyGroup>
-    <TclOpts Condition="$(Configuration) == 'Debug'">symbols</TclOpts>
+    <TclOpts>ucrt</TclOpts>
+    <TclOpts Condition="$(Configuration) == 'Debug'">symbols,ucrt</TclOpts>
     <TclDirs>INSTALLDIR="$(OutDir.TrimEnd(`\`))" INSTALL_DIR="$(OutDir.TrimEnd(`\`))"</TclDirs>
     <DebugFlags Condition="'$(Configuration)' == 'Debug'">DEBUGFLAGS="-wd4456 -wd4457 -wd4458 -wd4459 -wd4996"</DebugFlags>
     <NMakeBuildCommandLine>setlocal
diff --git a/PCbuild/tix.vcxproj b/PCbuild/tix.vcxproj
--- a/PCbuild/tix.vcxproj
+++ b/PCbuild/tix.vcxproj
@@ -56,11 +56,9 @@
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   
   <PropertyGroup>
-    <TkOpts>msvcrt</TkOpts>
-    <TkOpts Condition="$(Configuration) == 'Debug'">symbols,msvcrt</TkOpts>
     <TixDirs>BUILDDIRTOP="$(BuildDirTop)" TCL_DIR="$(tclDir.TrimEnd(`\`))" TK_DIR="$(tkDir.TrimEnd(`\`))" INSTALL_DIR="$(OutDir.TrimEnd(`\`))"</TixDirs>
-    <DebugFlags Condition="'$(Configuration)' == 'Debug'">DEBUG=1 NODEBUG=0 TCL_DBGX=g DEBUGFLAGS="-wd4456 -wd4457 -wd4458 -wd4459 -wd4996"</DebugFlags>
-    <DebugFlags Condition="'$(Configuration)' != 'Debug'">DEBUG=0 NODEBUG=1</DebugFlags>
+    <DebugFlags Condition="'$(Configuration)' == 'Debug'">DEBUG=1 NODEBUG=0 UCRT=1 TCL_DBGX=g TK_DBGX=g</DebugFlags>
+    <DebugFlags Condition="'$(Configuration)' != 'Debug'">DEBUG=0 NODEBUG=1 UCRT=1</DebugFlags>
     <NMakeBuildCommandLine>setlocal
 @(ExpectedOutputs->'if not exist "%(FullPath)" goto build','
 ')
diff --git a/PCbuild/tk.vcxproj b/PCbuild/tk.vcxproj
--- a/PCbuild/tk.vcxproj
+++ b/PCbuild/tk.vcxproj
@@ -60,8 +60,8 @@
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   
   <PropertyGroup>
-    <TkOpts>msvcrt</TkOpts>
-    <TkOpts Condition="$(Configuration) == 'Debug'">symbols,msvcrt</TkOpts>
+    <TkOpts>ucrt</TkOpts>
+    <TkOpts Condition="$(Configuration) == 'Debug'">symbols,ucrt</TkOpts>
     <TkDirs>TCLDIR="$(tclDir.TrimEnd(`\`))" INSTALLDIR="$(OutDir.TrimEnd(`\`))"</TkDirs>
     <DebugFlags Condition="'$(Configuration)' == 'Debug'">DEBUGFLAGS="-wd4456 -wd4457 -wd4458 -wd4459 -wd4996"</DebugFlags>
     <NMakeBuildCommandLine>setlocal