diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -6490,6 +6490,12 @@
     }
 
     CmdArgs.push_back(LanguageStandard.data());
+
+    // MSVC enables /Zc:alignedNew by default for C++17
+    if (!Args.getLastArg(options::OPT_faligned_allocation,
+                         options::OPT_fno_aligned_allocation) &&
+        LanguageStandard == "-std=c++17")
+      CmdArgs.push_back("-faligned-allocation");
   }
 
   Args.addOptInFlag(CmdArgs, options::OPT_fborland_extensions,
@@ -6618,6 +6624,13 @@
   Args.addOptInFlag(CmdArgs, options::OPT_frelaxed_template_template_args,
                     options::OPT_fno_relaxed_template_template_args);
 
+  // MSVC turns on /Zc:sizedDealloc by default. Honor whatever is passed
+  // on the cmdline.
+  if (IsWindowsMSVC &&
+      !Args.getLastArg(options::OPT_fsized_deallocation,
+                       options::OPT_fno_sized_deallocation))
+    CmdArgs.push_back("-fsized-deallocation");
+
   // -fsized-deallocation is off by default, as it is an ABI-breaking change for
   // most platforms.
   Args.addOptInFlag(CmdArgs, options::OPT_fsized_deallocation,
diff --git a/clang/test/Driver/cl-zc.cpp b/clang/test/Driver/cl-zc.cpp
--- a/clang/test/Driver/cl-zc.cpp
+++ b/clang/test/Driver/cl-zc.cpp
@@ -1,6 +1,12 @@
 // Note: %s must be preceded by --, otherwise it may be interpreted as a
 // command-line option, e.g. on Mac where %s is commonly under /Users.
 
+// RUN: %clang_cl /c /std:c++17 -### -- %s 2>&1 | FileCheck -check-prefix=ALIGNED-NEW-CPP17-DEFAULT %s
+// ALIGNED-NEW-CPP17-DEFAULT: "-faligned-allocation"
+
+// RUN: %clang_cl /c -### -- %s 2>&1 | FileCheck -check-prefix=SIZED-DEALLOC-DEFAULT %s
+// SIZED-DEALLOC-DEFAULT: "-fsized-deallocation"
+
 // RUN: %clang_cl /c -### -- %s 2>&1 | FileCheck -check-prefix=TRIGRAPHS-DEFAULT %s
 // cc1 will disable trigraphs for -fms-compatibility as long as -ftrigraphs
 // isn't explicitly passed.