diff --git a/clang/lib/Driver/ToolChains/WebAssembly.cpp b/clang/lib/Driver/ToolChains/WebAssembly.cpp
--- a/clang/lib/Driver/ToolChains/WebAssembly.cpp
+++ b/clang/lib/Driver/ToolChains/WebAssembly.cpp
@@ -106,17 +106,17 @@
 
   getProgramPaths().push_back(getDriver().getInstalledDir());
 
-  if (getTriple().getOS() == llvm::Triple::UnknownOS) {
+  if (getTriple().getOS() != llvm::Triple::UnknownOS) {
     // Theoretically an "unknown" OS should mean no standard libraries, however
     // it could also mean that a custom set of libraries is in use, so just add
     // /lib to the search path. Disable multiarch in this case, to discourage
     // paths containing "unknown" from acquiring meanings.
-    getFilePaths().push_back(getDriver().SysRoot + "/lib");
-  } else {
     const std::string MultiarchTriple =
         getMultiarchTriple(getDriver(), Triple, getDriver().SysRoot);
     getFilePaths().push_back(getDriver().SysRoot + "/lib/" + MultiarchTriple);
   }
+
+  getFilePaths().push_back(getDriver().SysRoot + "/lib");
 }
 
 bool WebAssembly::IsMathErrnoDefault() const { return false; }