Index: source/Commands/CommandObjectSettings.cpp
===================================================================
--- source/Commands/CommandObjectSettings.cpp
+++ source/Commands/CommandObjectSettings.cpp
@@ -38,7 +38,9 @@
 public:
   CommandObjectSettingsSet(CommandInterpreter &interpreter)
       : CommandObjectRaw(interpreter, "settings set",
-                         "Set the value of the specified debugger setting."),
+                         "Set the value of the specified debugger setting. "
+                         "Providing no value is equivalent to \"settings "
+                         "clear\"."),
         m_options() {
     CommandArgumentEntry arg1;
     CommandArgumentEntry arg2;
@@ -185,7 +187,7 @@
       return false;
 
     const size_t argc = cmd_args.GetArgumentCount();
-    if ((argc < 2) && (!m_options.m_global)) {
+    if ((argc < 1) && (!m_options.m_global)) {
       result.AppendError("'settings set' takes more arguments");
       result.SetStatus(eReturnStatusFailed);
       return false;
@@ -199,6 +201,18 @@
       return false;
     }
 
+    // A missing value corresponds to clearing the setting.
+    if (argc == 1) {
+      Status error(m_interpreter.GetDebugger().SetPropertyValue(
+          &m_exe_ctx, eVarSetOperationClear, var_name, llvm::StringRef()));
+      if (error.Fail()) {
+        result.AppendError(error.AsCString());
+        result.SetStatus(eReturnStatusFailed);
+        return false;
+      }
+      return result.Succeeded();
+    }
+
     // Split the raw command into var_name and value pair.
     llvm::StringRef raw_str(command);
     std::string var_value_string = raw_str.split(var_name).second.str();