Index: clang/lib/Driver/ToolChains/WebAssembly.cpp
===================================================================
--- clang/lib/Driver/ToolChains/WebAssembly.cpp
+++ clang/lib/Driver/ToolChains/WebAssembly.cpp
@@ -528,10 +528,12 @@
 
   // First add the per-target include path if the OS is known.
   if (IsKnownOs) {
-    std::string TargetDir = LibPath + "/" + MultiarchTriple + "/c++/" + Version;
+    std::string TargetDir = LibPath + "/c++/" + Version + "/" + MultiarchTriple;
     addSystemInclude(DriverArgs, CC1Args, TargetDir);
   }
 
   // Second add the generic one.
   addSystemInclude(DriverArgs, CC1Args, LibPath + "/c++/" + Version);
+  // Third the backward one.
+  addSystemInclude(DriverArgs, CC1Args, LibPath + "/c++/" + Version + "/backward");
 }
Index: clang/test/Driver/wasm-toolchain.cpp
===================================================================
--- clang/test/Driver/wasm-toolchain.cpp
+++ clang/test/Driver/wasm-toolchain.cpp
@@ -80,8 +80,9 @@
 // COMPILE_STDCXX: clang{{.*}}" "-cc1"
 // COMPILE_STDCXX: "-resource-dir" "[[RESOURCE_DIR:[^"]*]]"
 // COMPILE_STDCXX: "-isysroot" "[[SYSROOT:[^"]+]]"
-// COMPILE_STDCXX: "-internal-isystem" "[[SYSROOT:[^"]+]]/include/wasm32-wasi/c++/4.8"
+// COMPILE_STDCXX: "-internal-isystem" "[[SYSROOT:[^"]+]]/include/c++/4.8/wasm32-wasi"
 // COMPILE_STDCXX: "-internal-isystem" "[[SYSROOT:[^"]+]]/include/c++/4.8"
+// COMPILE_STDCXX: "-internal-isystem" "[[SYSROOT:[^"]+]]/include/c++/4.8/backward"
 // COMPILE_STDCXX: "-internal-isystem" "[[RESOURCE_DIR]]{{(/|\\\\)}}include"
 // COMPILE_STDCXX: "-internal-isystem" "[[SYSROOT:[^"]+]]/include/wasm32-wasi"
 // COMPILE_STDCXX: "-internal-isystem" "[[SYSROOT:[^"]+]]/include"