diff --git a/build.vc15/mpir-tests.sln b/build.vc15/mpir-tests.sln
index a0855263..77c83952 100644
--- a/build.vc15/mpir-tests.sln
+++ b/build.vc15/mpir-tests.sln
@@ -435,6 +435,8 @@ Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "mpz.next_prime_candidate",
 EndProject
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "mpz.limbs", "mpir-tests\mpz.limbs\mpz.limbs.vcxproj", "{1F36B6D7-4504-4B2B-BABC-7CFBEC62029B}"
 EndProject
+Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "mpn.sizeinbase", "mpir-tests\mpn.sizeinbase\mpn.sizeinbase.vcxproj", "{935A51B1-BFEB-4864-A11A-1B436811C52D}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Win32 = Debug|Win32
@@ -1663,6 +1665,14 @@ Global
 		{1F36B6D7-4504-4B2B-BABC-7CFBEC62029B}.Release|Win32.Build.0 = Release|Win32
 		{1F36B6D7-4504-4B2B-BABC-7CFBEC62029B}.Release|x64.ActiveCfg = Release|x64
 		{1F36B6D7-4504-4B2B-BABC-7CFBEC62029B}.Release|x64.Build.0 = Release|x64
+		{935A51B1-BFEB-4864-A11A-1B436811C52D}.Debug|Win32.ActiveCfg = Debug|Win32
+		{935A51B1-BFEB-4864-A11A-1B436811C52D}.Debug|Win32.Build.0 = Debug|Win32
+		{935A51B1-BFEB-4864-A11A-1B436811C52D}.Debug|x64.ActiveCfg = Debug|x64
+		{935A51B1-BFEB-4864-A11A-1B436811C52D}.Debug|x64.Build.0 = Debug|x64
+		{935A51B1-BFEB-4864-A11A-1B436811C52D}.Release|Win32.ActiveCfg = Release|Win32
+		{935A51B1-BFEB-4864-A11A-1B436811C52D}.Release|Win32.Build.0 = Release|Win32
+		{935A51B1-BFEB-4864-A11A-1B436811C52D}.Release|x64.ActiveCfg = Release|x64
+		{935A51B1-BFEB-4864-A11A-1B436811C52D}.Release|x64.Build.0 = Release|x64
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
diff --git a/build.vc15/mpir-tests/mpn.sizeinbase/mpn.sizeinbase.vcxproj b/build.vc15/mpir-tests/mpn.sizeinbase/mpn.sizeinbase.vcxproj
new file mode 100644
index 00000000..6adc10e8
--- /dev/null
+++ b/build.vc15/mpir-tests/mpn.sizeinbase/mpn.sizeinbase.vcxproj
@@ -0,0 +1,179 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project DefaultTargets="Build" ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup Label="ProjectConfigurations">
+    <ProjectConfiguration Include="Debug|Win32">
+      <Configuration>Debug</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Debug|x64">
+      <Configuration>Debug</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|Win32">
+      <Configuration>Release</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|x64">
+      <Configuration>Release</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+  </ItemGroup>
+  <PropertyGroup Label="Globals">
+    <RootNamespace>mpn.sizeinbase</RootNamespace>
+    <Keyword>Win32Proj</Keyword>
+    <WindowsTargetPlatformVersion>8.1</WindowsTargetPlatformVersion>
+    <ProjectGuid>{935A51B1-BFEB-4864-A11A-1B436811C52D}</ProjectGuid>
+  </PropertyGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'" Label="Configuration">
+    <ConfigurationType>Application</ConfigurationType>
+    <PlatformToolset>v141</PlatformToolset>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'" Label="Configuration">
+    <ConfigurationType>Application</ConfigurationType>
+    <PlatformToolset>v141</PlatformToolset>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'" Label="Configuration">
+    <ConfigurationType>Application</ConfigurationType>
+    <PlatformToolset>v141</PlatformToolset>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'" Label="Configuration">
+    <ConfigurationType>Application</ConfigurationType>
+    <PlatformToolset>v141</PlatformToolset>
+  </PropertyGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
+  <ImportGroup Label="ExtensionSettings">
+  </ImportGroup>
+  <ImportGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'" Label="PropertySheets">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" />
+    <Import Project="..\..\test-config.props" />
+  </ImportGroup>
+  <ImportGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'" Label="PropertySheets">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" />
+    <Import Project="..\..\test-config.props" />
+  </ImportGroup>
+  <ImportGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'" Label="PropertySheets">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" />
+    <Import Project="..\..\test-config.props" />
+  </ImportGroup>
+  <ImportGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'" Label="PropertySheets">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" />
+    <Import Project="..\..\test-config.props" />
+  </ImportGroup>
+  <PropertyGroup Label="UserMacros" />
+  <PropertyGroup>
+    <_ProjectFileVersion>10.0.21006.1</_ProjectFileVersion>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
+    <OutDir>$(SolutionDir)$(Platform)\$(Configuration)\</OutDir>
+    <IntDir>$(Platform)\$(Configuration)\</IntDir>
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+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
+    <OutDir>$(SolutionDir)$(Platform)\$(Configuration)\</OutDir>
+    <IntDir>$(Platform)\$(Configuration)\</IntDir>
+  </PropertyGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
+    <PreBuildEvent>
+      <Command>cd ..\..\..\build.vc 
+check_config $(Platform) $(Configuration) 15</Command>
+    </PreBuildEvent>
+    <ClCompile>
+      <Optimization>Disabled</Optimization>
+      <PreprocessorDefinitions>_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PrecompiledHeader>
+      </PrecompiledHeader>
+      <CompileAs>Default</CompileAs>
+    </ClCompile>
+    <Link>
+      <SubSystem>Console</SubSystem>
+      <RandomizedBaseAddress>false</RandomizedBaseAddress>
+      <DataExecutionPrevention>
+      </DataExecutionPrevention>
+      <TargetMachine>MachineX86</TargetMachine>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
+    <PreBuildEvent>
+      <Command>cd ..\..\..\build.vc 
+check_config $(Platform) $(Configuration) 15</Command>
+    </PreBuildEvent>
+    <Midl>
+      <TargetEnvironment>X64</TargetEnvironment>
+    </Midl>
+    <ClCompile>
+      <PreprocessorDefinitions>_WIN64;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PrecompiledHeader>
+      </PrecompiledHeader>
+      <CompileAs>Default</CompileAs>
+    </ClCompile>
+    <Link>
+      <SubSystem>Console</SubSystem>
+      <RandomizedBaseAddress>false</RandomizedBaseAddress>
+      <DataExecutionPrevention>
+      </DataExecutionPrevention>
+      <TargetMachine>MachineX64</TargetMachine>
+      <GenerateDebugInformation>Debug</GenerateDebugInformation>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
+    <PreBuildEvent>
+      <Command>cd ..\..\..\build.vc 
+check_config $(Platform) $(Configuration) 15</Command>
+    </PreBuildEvent>
+    <ClCompile>
+      <Optimization>Full</Optimization>
+      <PreprocessorDefinitions>NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PrecompiledHeader>
+      </PrecompiledHeader>
+      <CompileAs>Default</CompileAs>
+    </ClCompile>
+    <Link>
+      <SubSystem>Console</SubSystem>
+      <OptimizeReferences>true</OptimizeReferences>
+      <EnableCOMDATFolding>true</EnableCOMDATFolding>
+      <RandomizedBaseAddress>false</RandomizedBaseAddress>
+      <DataExecutionPrevention>
+      </DataExecutionPrevention>
+      <TargetMachine>MachineX86</TargetMachine>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'">
+    <PreBuildEvent>
+      <Command>cd ..\..\..\build.vc 
+check_config $(Platform) $(Configuration) 15</Command>
+    </PreBuildEvent>
+    <Midl>
+      <TargetEnvironment>X64</TargetEnvironment>
+    </Midl>
+    <ClCompile>
+      <Optimization>Full</Optimization>
+      <PreprocessorDefinitions>_WIN64;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PrecompiledHeader>
+      </PrecompiledHeader>
+      <CompileAs>Default</CompileAs>
+      <AdditionalIncludeDirectories>$(MPDIR);$(SolutionDir)..\tests</AdditionalIncludeDirectories>
+    </ClCompile>
+    <Link>
+      <SubSystem>Console</SubSystem>
+      <OptimizeReferences>true</OptimizeReferences>
+      <EnableCOMDATFolding>true</EnableCOMDATFolding>
+      <RandomizedBaseAddress>false</RandomizedBaseAddress>
+      <DataExecutionPrevention>
+      </DataExecutionPrevention>
+      <TargetMachine>MachineX64</TargetMachine>
+      <GenerateDebugInformation>No</GenerateDebugInformation>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemGroup>
+    <ClCompile Include="..\..\..\tests\mpn\t-sizeinbase.c" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\add-test-lib\add-test-lib.vcxproj">
+      <Project>{a742d3d1-6956-4f85-bfd6-b0e7b477041d}</Project>
+      <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
+    </ProjectReference>
+  </ItemGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
+  <ImportGroup Label="ExtensionTargets">
+  </ImportGroup>
+</Project>
\ No newline at end of file