diff --git a/Solutions/conformance.props b/Solutions/conformance.props
new file mode 100644
index 000000000..79e1ae779
--- /dev/null
+++ b/Solutions/conformance.props
@@ -0,0 +1,23 @@
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <!--
+    MSVC conformance mode (/permissive-) for the native SDK library projects
+    that import this file (win32-lib, win32-dll, win32-mini-lib, win32-mini-dll,
+    net40), so non-standard constructs are caught at build time. See issue #255.
+
+    This is imported explicitly per-project rather than from the shared
+    Solutions/build.props, because build.props is also pulled in by vendored
+    sqlite/zlib, the test projects (gtest/gmock/UnitTests/FuncTests), and the
+    samples - none of which we want to force into conformance mode. UWP /
+    Windows Store SDK projects (win10-*) intentionally do not import this file
+    because /permissive- is incompatible with C++/CX (/ZW); their shared SDK
+    sources are still conformance-checked through the win32 library builds.
+
+    Imported late (after the project's own ItemDefinitionGroups) so this
+    ConformanceMode setting wins.
+  -->
+  <ItemDefinitionGroup>
+    <ClCompile>
+      <ConformanceMode>true</ConformanceMode>
+    </ClCompile>
+  </ItemDefinitionGroup>
+</Project>
diff --git a/Solutions/net40/net40.vcxproj b/Solutions/net40/net40.vcxproj
index ec55747a0..d21aede17 100644
--- a/Solutions/net40/net40.vcxproj
+++ b/Solutions/net40/net40.vcxproj
@@ -290,6 +290,7 @@
     </ProjectReference>
   </ItemGroup>
   <Import Project="$(SolutionDir)\build.props" Condition="Exists('$(SolutionDir)\build.props')" />
+  <Import Project="$(SolutionDir)\conformance.props" Condition="Exists('$(SolutionDir)\conformance.props')" />
   <Import Project="$(SolutionDir)\build.net40.props" Condition="Exists('$(SolutionDir)\build.net40.props')" />
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
diff --git a/Solutions/win32-dll/win32-dll.vcxproj b/Solutions/win32-dll/win32-dll.vcxproj
index 026356130..b01b9e690 100644
--- a/Solutions/win32-dll/win32-dll.vcxproj
+++ b/Solutions/win32-dll/win32-dll.vcxproj
@@ -337,6 +337,7 @@
     </ProjectReference>
   </ItemGroup>
   <Import Project="$(SolutionDir)\build.props" Condition="Exists('$(SolutionDir)\build.props')" />
+  <Import Project="$(SolutionDir)\conformance.props" Condition="Exists('$(SolutionDir)\conformance.props')" />
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
diff --git a/Solutions/win32-lib/win32-lib.vcxproj b/Solutions/win32-lib/win32-lib.vcxproj
index 90602e232..1b9fb6a7c 100644
--- a/Solutions/win32-lib/win32-lib.vcxproj
+++ b/Solutions/win32-lib/win32-lib.vcxproj
@@ -537,6 +537,7 @@
     </Lib>
   </ItemDefinitionGroup>
   <Import Project="$(SolutionDir)\build.props" Condition="Exists('$(SolutionDir)\build.props')" />
+  <Import Project="$(SolutionDir)\conformance.props" Condition="Exists('$(SolutionDir)\conformance.props')" />
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
diff --git a/Solutions/win32-mini-dll/win32-mini-dll.vcxproj b/Solutions/win32-mini-dll/win32-mini-dll.vcxproj
index ce42cf020..fe923aee2 100644
--- a/Solutions/win32-mini-dll/win32-mini-dll.vcxproj
+++ b/Solutions/win32-mini-dll/win32-mini-dll.vcxproj
@@ -390,6 +390,7 @@
     </Lib>
   </ItemDefinitionGroup>
   <Import Project="$(SolutionDir)\build.props" Condition="Exists('$(SolutionDir)\build.props')" />
+  <Import Project="$(SolutionDir)\conformance.props" Condition="Exists('$(SolutionDir)\conformance.props')" />
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
diff --git a/Solutions/win32-mini-lib/win32-mini-lib.vcxproj b/Solutions/win32-mini-lib/win32-mini-lib.vcxproj
index e720328fd..700623d89 100644
--- a/Solutions/win32-mini-lib/win32-mini-lib.vcxproj
+++ b/Solutions/win32-mini-lib/win32-mini-lib.vcxproj
@@ -678,6 +678,7 @@
     </Lib>
   </ItemDefinitionGroup>
   <Import Project="$(SolutionDir)\build.props" Condition="Exists('$(SolutionDir)\build.props')" />
+  <Import Project="$(SolutionDir)\conformance.props" Condition="Exists('$(SolutionDir)\conformance.props')" />
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
diff --git a/lib/shared/EventPropertiesCX.cpp b/lib/shared/EventPropertiesCX.cpp
index 9c212d919..889965f6d 100644
--- a/lib/shared/EventPropertiesCX.cpp
+++ b/lib/shared/EventPropertiesCX.cpp
@@ -26,7 +26,7 @@ namespace Microsoft {
                     FromPlatformMap(propertiesMap, properties);
                     FromPlatformMap(this->PIITags, piiTags);
 
-                    for (map<string, T>::iterator it = properties.begin(); it != properties.end(); ++it)
+                    for (typename map<string, T>::iterator it = properties.begin(); it != properties.end(); ++it)
                     {
                         MAT::PiiKind piiType = MAT::PiiKind_None;
                         auto tag = piiTags.find(it->first);
diff --git a/lib/shared/PlatformHelpers.h b/lib/shared/PlatformHelpers.h
index 47d1e723d..222ee0024 100644
--- a/lib/shared/PlatformHelpers.h
+++ b/lib/shared/PlatformHelpers.h
@@ -105,6 +105,11 @@ namespace Microsoft {
                 void ThrowPlatformInvalidArgumentException(String^ message);
                 void ThrowPlatformException(String^ message);
 
+                // Forward declaration so the FromPlatformMap templates below can
+                // resolve this helper under /permissive- two-phase name lookup
+                // (the definition appears later in this header).
+                std::string FromPlatformString(String^ platformString);
+
                 // Defining the template function in the header file eliminates the need in additional linker definitions.
                 // platformmaptype can be read-only or editable platform map.
                 template <typename K1, typename V1, typename K2, typename V2, template<typename, typename> class platformmaptype>