diff --git a/DirectXTex/BC6HBC7.cpp b/DirectXTex/BC6HBC7.cpp
index 37ff900..f87dc63 100644
--- a/DirectXTex/BC6HBC7.cpp
+++ b/DirectXTex/BC6HBC7.cpp
@@ -1195,7 +1195,11 @@ namespace
 
         // Find Min and Max points, as starting point
         HDRColorA X, Y;
+#if (__cplusplus >= 201703L)
+        if constexpr (ishdr)
+#else
         if (ishdr)
+#endif
         {
             X = HDRColorA{ FLT_MAX, FLT_MAX, FLT_MAX, 0.0f };
             Y = HDRColorA{ -FLT_MAX, -FLT_MAX, -FLT_MAX, 0.0f };
diff --git a/DirectXTex/DirectXTexConvert.cpp b/DirectXTex/DirectXTexConvert.cpp
index e75b8c4..3660177 100644
--- a/DirectXTex/DirectXTexConvert.cpp
+++ b/DirectXTex/DirectXTexConvert.cpp
@@ -3263,10 +3263,11 @@ void DirectX::Internal::ConvertScanline(
                         break;
                     }
 
-#ifdef _MSC_VER
+#if (__cplusplus >= 201703L)
+                    [[fallthrough]];
+#elif defined(_MSC_VER)
                     __fallthrough;
-#endif
-#ifdef __clang__
+#elif defined(__clang__)
                     [[clang::fallthrough]];
 #endif
 
@@ -3552,10 +3553,11 @@ void DirectX::Internal::ConvertScanline(
                     break;
                 }
 
-#ifdef _MSC_VER
+#if (__cplusplus >= 201703L)
+                [[fallthrough]];
+#elif defined(_MSC_VER)
                 __fallthrough;
-#endif
-#ifdef __clang__
+#elif defined(__clang__)
                 [[clang::fallthrough]];
 #endif
 
@@ -3650,10 +3652,11 @@ void DirectX::Internal::ConvertScanline(
                         break;
                     }
 
-#ifdef _MSC_VER
+#if (__cplusplus >= 201703L)
+                    [[fallthrough]];
+#elif defined(_MSC_VER)
                     __fallthrough;
-#endif
-#ifdef __clang__
+#elif defined(__clang__)
                     [[clang::fallthrough]];
 #endif