diff --git a/src/util/system.cpp b/src/util/system.cpp
--- a/src/util/system.cpp
+++ b/src/util/system.cpp
@@ -456,6 +456,15 @@
         SaveErrors(read_errors, errors);
         return false;
     }
+    for (const auto &setting : m_settings.rw_settings) {
+        std::string section;
+        std::string key = setting.first;
+        // Split setting key into section and argname
+        (void)InterpretOption(section, key, /* value */ {});
+        if (!GetArgFlags('-' + key)) {
+            LogPrintf("Ignoring unknown rw_settings value %s\n", setting.first);
+        }
+    }
     return true;
 }
 
diff --git a/test/functional/feature_settings.py b/test/functional/feature_settings.py
--- a/test/functional/feature_settings.py
+++ b/test/functional/feature_settings.py
@@ -33,20 +33,26 @@
             json.dump({"string": "string", "num": 5, "bool": True,
                        "null": None, "list": [6, 7]}, fp)
         with node.assert_debug_log(expected_msgs=[
+                'Ignoring unknown rw_settings value bool',
+                'Ignoring unknown rw_settings value list',
+                'Ignoring unknown rw_settings value null',
+                'Ignoring unknown rw_settings value num',
+                'Ignoring unknown rw_settings value string',
                 'Setting file arg: string = "string"',
                 'Setting file arg: num = 5',
                 'Setting file arg: bool = true',
                 'Setting file arg: null = null',
-                'Setting file arg: list = [6,7]']):
+                'Setting file arg: list = [6,7]',
+        ]):
             self.start_node(0)
             self.stop_node(0)
 
         # Assert settings are unchanged after shutdown
         with settings.open() as fp:
             assert_equal(
-                json.load(fp), {
-                    "string": "string", "num": 5, "bool": True, "null": None, "list": [
-                        6, 7]})
+                json.load(fp),
+                {"string": "string", "num": 5, "bool": True, "null": None,
+                 "list": [6, 7]})
 
         # Test invalid json
         with settings.open("w") as fp: