diff --git a/core/src/main/java/org/elasticsearch/plugins/PluginsService.java b/core/src/main/java/org/elasticsearch/plugins/PluginsService.java
index 762d497e832..1947953c35d 100644
--- a/core/src/main/java/org/elasticsearch/plugins/PluginsService.java
+++ b/core/src/main/java/org/elasticsearch/plugins/PluginsService.java
@@ -202,9 +202,18 @@ public class PluginsService extends AbstractComponent {
     }
 
     public Settings updatedSettings() {
+        Map<String, String> foundSettings = new HashMap<>();
         final Settings.Builder builder = Settings.settingsBuilder();
         for (Tuple<PluginInfo, Plugin> plugin : plugins) {
-            builder.put(plugin.v2().additionalSettings());
+            Settings settings = plugin.v2().additionalSettings();
+            for (String setting : settings.getAsMap().keySet()) {
+                String oldPlugin = foundSettings.put(setting, plugin.v1().getName());
+                if (oldPlugin != null) {
+                    throw new IllegalArgumentException("Cannot have additional setting [" + setting + "] " +
+                        "in plugin " + plugin.v1().getName() + ", already added in plugin " + oldPlugin);
+                }
+            }
+            builder.put(settings);
         }
         return builder.put(this.settings).build();
     }
diff --git a/core/src/test/java/org/elasticsearch/plugins/PluginsServiceTests.java b/core/src/test/java/org/elasticsearch/plugins/PluginsServiceTests.java
new file mode 100644
index 00000000000..5b0ea2d4eb3
--- /dev/null
+++ b/core/src/test/java/org/elasticsearch/plugins/PluginsServiceTests.java
@@ -0,0 +1,85 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.plugins;
+
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.env.Environment;
+import org.elasticsearch.index.store.IndexStoreModule;
+import org.elasticsearch.test.ESTestCase;
+
+public class PluginsServiceTests extends ESTestCase {
+    public static class AdditionalSettingsPlugin1 extends AbstractPlugin {
+        @Override
+        public String name() {
+            return "additional-settings1";
+        }
+        @Override
+        public String description() {
+            return "adds additional setting 'foo.bar'";
+        }
+        @Override
+        public Settings additionalSettings() {
+            return Settings.builder().put("foo.bar", "1").put(IndexStoreModule.STORE_TYPE, IndexStoreModule.Type.MMAPFS.getSettingsKey()).build();
+        }
+    }
+    public static class AdditionalSettingsPlugin2 extends AbstractPlugin {
+        @Override
+        public String name() {
+            return "additional-settings2";
+        }
+        @Override
+        public String description() {
+            return "adds additional setting 'foo.bar'";
+        }
+        @Override
+        public Settings additionalSettings() {
+            return Settings.builder().put("foo.bar", "2").build();
+        }
+    }
+
+    public void testAdditionalSettings() {
+        Settings settings = Settings.builder()
+            .put("path.home", createTempDir())
+            .put("my.setting", "test")
+            .put(IndexStoreModule.STORE_TYPE, IndexStoreModule.Type.SIMPLEFS.getSettingsKey())
+            .putArray("plugin.types", AdditionalSettingsPlugin1.class.getName()).build();
+        PluginsService service = new PluginsService(settings, new Environment(settings));
+        Settings newSettings = service.updatedSettings();
+        assertEquals("test", newSettings.get("my.setting")); // previous settings still exist
+        assertEquals("1", newSettings.get("foo.bar")); // added setting exists
+        assertEquals(IndexStoreModule.Type.SIMPLEFS.getSettingsKey(), newSettings.get(IndexStoreModule.STORE_TYPE)); // does not override pre existing settings
+    }
+
+    public void testAdditionalSettingsClash() {
+        Settings settings = Settings.builder()
+            .put("path.home", createTempDir())
+            .putArray("plugin.types", AdditionalSettingsPlugin1.class.getName(), AdditionalSettingsPlugin2.class.getName()).build();
+        PluginsService service = new PluginsService(settings, new Environment(settings));
+        try {
+            service.updatedSettings();
+            fail("Expected exception when building updated settings");
+        } catch (IllegalArgumentException e) {
+            String msg = e.getMessage();
+            assertTrue(msg, msg.contains("Cannot have additional setting [foo.bar]"));
+            assertTrue(msg, msg.contains("plugin additional-settings1"));
+            assertTrue(msg, msg.contains("plugin additional-settings2"));
+        }
+    }
+}