diff --git a/lld/test/wasm/driver.s b/lld/test/wasm/driver.s
--- a/lld/test/wasm/driver.s
+++ b/lld/test/wasm/driver.s
@@ -5,6 +5,9 @@
   .functype _start () -> ()
   end_function
 
+# RUN: not wasm-ld %t -o 2>&1 | FileCheck --check-prefix=NO_O_VAL %s
+# NO_O_VAL: error: -o: missing argument
+
 # RUN: not wasm-ld -o %t.exe 2>&1 | FileCheck -check-prefix=IN %s
 # IN: error: no input files
 
diff --git a/lld/wasm/Driver.cpp b/lld/wasm/Driver.cpp
--- a/lld/wasm/Driver.cpp
+++ b/lld/wasm/Driver.cpp
@@ -184,6 +184,9 @@
   args = this->ParseArgs(vec, missingIndex, missingCount);
 
   handleColorDiagnostics(args);
+  if (missingCount)
+    error(Twine(args.getArgString(missingIndex)) + ": missing argument");
+
   for (auto *arg : args.filtered(OPT_UNKNOWN))
     error("unknown argument: " + arg->getAsString(args));
   return args;
@@ -810,6 +813,12 @@
   });
 }
 
+static const char *getReproduceOption(opt::InputArgList &args) {
+  if (auto *arg = args.getLastArg(OPT_reproduce))
+    return arg->getValue();
+  return getenv("LLD_REPRODUCE");
+}
+
 static bool isKnownZFlag(StringRef s) {
   // For now, we only support a very limited set of -z flags
   return s.startswith("stack-size=");
@@ -847,8 +856,8 @@
   }
 
   // Handle --reproduce
-  if (auto *arg = args.getLastArg(OPT_reproduce)) {
-    StringRef path = arg->getValue();
+  // Note that --reproduce is a debug option so you can ignore it
+  if (const char *path = getReproduceOption(args)) {
     Expected<std::unique_ptr<TarWriter>> errOrWriter =
         TarWriter::create(path, path::stem(path));
     if (errOrWriter) {
diff --git a/lld/wasm/Options.td b/lld/wasm/Options.td
--- a/lld/wasm/Options.td
+++ b/lld/wasm/Options.td
@@ -1,5 +1,18 @@
 include "llvm/Option/OptParser.td"
 
+// Convenience classes for long options which only accept two dashes. For lld
+// specific or newer long options, we prefer two dashes to avoid collision with
+// short options. For many others, we have to accept both forms to be compatible
+// with GNU ld.
+class FF<string name> : Flag<["--"], name>;
+class JJ<string name>: Joined<["--"], name>;
+
+multiclass EEq<string name, string help> {
+  def NAME: Separate<["--"], name>;
+  def NAME # _eq: Joined<["--"], name # "=">, Alias<!cast<Separate>(NAME)>,
+    HelpText<help>;
+}
+
 // For options whose names are multiple letters, either one dash or
 // two can precede the option name except those that start with 'o'.
 class F<string name>: Flag<["--", "-"], name>;
@@ -99,7 +112,7 @@
 
 def relocatable: F<"relocatable">, HelpText<"Create relocatable object file">;
 
-defm reproduce: Eq<"reproduce", "Dump linker invocation and input files for debugging">;
+defm reproduce: EEq<"reproduce", "Dump linker invocation and input files for debugging">;
 
 defm rsp_quoting: Eq<"rsp-quoting", "Quoting style for response files">,
   MetaVarName<"[posix,windows]">;