Index: lld/MachO/DriverUtils.cpp
===================================================================
--- lld/MachO/DriverUtils.cpp
+++ lld/MachO/DriverUtils.cpp
@@ -75,8 +75,14 @@
 
   handleColorDiagnostics(args);
 
-  for (opt::Arg *arg : args.filtered(OPT_UNKNOWN))
-    error("unknown argument: " + arg->getSpelling());
+  for (auto *arg : args.filtered(OPT_UNKNOWN)) {
+    std::string nearest;
+    if (findNearest(arg->getAsString(args), nearest) > 1)
+      error("unknown argument '" + arg->getAsString(args) + "'");
+    else
+      error("unknown argument '" + arg->getAsString(args) +
+            "', did you mean '" + nearest + "'");
+  }
   return args;
 }
 
Index: lld/test/MachO/color-diagnostics.test
===================================================================
--- lld/test/MachO/color-diagnostics.test
+++ lld/test/MachO/color-diagnostics.test
@@ -6,7 +6,7 @@
 # RUN: not %lld -xyz --color-diagnostics=always /nosuchfile 2>&1 \
 # RUN:   | FileCheck -check-prefix=COLOR %s
 
-# COLOR: {{lld: .\[0;31merror: .\[0munknown argument: -xyz}}
+# COLOR: {{lld: .\[0;31merror: .\[0munknown argument '-xyz'}}
 # COLOR: {{lld: .\[0;31merror: .\[0mcannot open /nosuchfile}}
 
 # RUN: not %lld --color-diagnostics=foobar 2>&1 | FileCheck -check-prefix=ERR %s
Index: lld/test/MachO/driver.test
===================================================================
--- /dev/null
+++ lld/test/MachO/driver.test
@@ -0,0 +1,4 @@
+# RUN: not %lld ---help 2>&1 | FileCheck -check-prefix=SPELLHELP %s
+SPELLHELP: error: unknown argument '---help', did you mean '--help'
+# FIXME: This should say "no input files" instead
+SPELLHELP: error: undefined symbol: _main
Index: lld/test/MachO/silent-ignore.test
===================================================================
--- lld/test/MachO/silent-ignore.test
+++ lld/test/MachO/silent-ignore.test
@@ -10,4 +10,4 @@
 RUN:   -ios_simulator_version_min 9.0.0 \
 RUN:   -sdk_version 13.2
 RUN: not %lld -v --not-an-ignored-argument 2>&1 | FileCheck %s
-CHECK: error: unknown argument: --not-an-ignored-argument
+CHECK: error: unknown argument '--not-an-ignored-argument'