diff --git a/src/mon/MonCommands.h b/src/mon/MonCommands.h
index 010e4c99ff4..a9055041e6c 100644
--- a/src/mon/MonCommands.h
+++ b/src/mon/MonCommands.h
@@ -211,6 +211,10 @@ COMMAND_WITH_FLAG("injectargs " \
 	     "name=injected_args,type=CephString,n=N",			\
 	     "inject config arguments into monitor", "mon", "rw", "cli,rest",
 	     FLAG(NOFORWARD))
+COMMAND("config set " \
+	"name=key,type=CephString name=value,type=CephString",
+	"Set a configuration option at runtime (not persistent)",
+	"mon", "rw", "cli,rest")
 COMMAND("status", "show cluster status", "mon", "r", "cli,rest")
 COMMAND("health name=detail,type=CephChoices,strings=detail,req=false", \
 	"show cluster health", "mon", "r", "cli,rest")
diff --git a/src/mon/Monitor.cc b/src/mon/Monitor.cc
index 7969df17f57..9ec308d7832 100644
--- a/src/mon/Monitor.cc
+++ b/src/mon/Monitor.cc
@@ -3261,6 +3261,14 @@ void Monitor::handle_command(MonOpRequestRef op)
     f->flush(rdata);
     r = 0;
     rs = "";
+  } else if (prefix == "config set") {
+    std::string key;
+    cmd_getval(cct, cmdmap, "key", key);
+    std::string val;
+    cmd_getval(cct, cmdmap, "value", val);
+    r = g_conf->set_val(key, val, true, &ss);
+    rs = ss.str();
+    goto out;
   } else if (prefix == "status" ||
 	     prefix == "health" ||
 	     prefix == "df") {