--- a/clang/lib/Driver/ToolChains/WebAssembly.cpp
+++ b/clang/lib/Driver/ToolChains/WebAssembly.cpp
@@ -369,6 +369,18 @@ ToolChain::RuntimeLibType WebAssembly::G
   return ToolChain::RLT_CompilerRT;
 }
 
+ToolChain::RuntimeLibType WebAssembly::GetRuntimeLibType(
+    const ArgList &Args) const {
+  if (Arg *A = Args.getLastArg(options::OPT_rtlib_EQ)) {
+    StringRef Value = A->getValue();
+    if (Value != "compiler-rt")
+      getDriver().Diag(clang::diag::err_drv_unsupported_rtlib_for_platform)
+          << Value << "WebAssembly";
+  }
+
+  return ToolChain::RLT_CompilerRT;
+}
+
 ToolChain::CXXStdlibType
 WebAssembly::GetCXXStdlibType(const ArgList &Args) const {
   if (Arg *A = Args.getLastArg(options::OPT_stdlib_EQ)) {
--- a/clang/lib/Driver/ToolChains/WebAssembly.h
+++ b/clang/lib/Driver/ToolChains/WebAssembly.h
@@ -61,6 +61,7 @@ private:
                         llvm::opt::ArgStringList &CC1Args,
                         Action::OffloadKind DeviceOffloadKind) const override;
   RuntimeLibType GetDefaultRuntimeLibType() const override;
+  RuntimeLibType GetRuntimeLibType(const llvm::opt::ArgList &Args) const override;
   CXXStdlibType GetCXXStdlibType(const llvm::opt::ArgList &Args) const override;
   void
   AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,