diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -599,14 +599,24 @@
   // TODO: Currently throws a Diagnostic for anything other than -W<error>,
   // this has to change when other -W<opt>'s are supported.
   if (args.hasArg(clang::driver::options::OPT_W_Joined)) {
-    if (args.getLastArgValue(clang::driver::options::OPT_W_Joined)
-            .equals("error")) {
-      res.setWarnAsErr(true);
-    } else {
-      const unsigned diagID =
-          diags.getCustomDiagID(clang::DiagnosticsEngine::Error,
-                                "Only `-Werror` is supported currently.");
-      diags.Report(diagID);
+    const auto wArgs =
+        args.getAllArgValues(clang::driver::options::OPT_W_Joined);
+    for (const auto &wArg : wArgs) {
+      if (wArg == "error") {
+        res.setWarnAsErr(true);
+      } else if (wArg == "extra") {
+        const unsigned id = diags.getCustomDiagID(
+            clang::DiagnosticsEngine::Warning,
+            "Argument `-Wextra` was ignored during compilation. Only `-Werror` "
+            "is supported currently.");
+        diags.Report(id);
+      } else {
+        const unsigned id =
+            diags.getCustomDiagID(clang::DiagnosticsEngine::Error,
+                                  "Only `-Werror` is supported currently.");
+        diags.Report(id);
+        break;
+      }
     }
   }