diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/config/ProjectConfigEntry.java b/gerrit-server/src/main/java/com/google/gerrit/server/config/ProjectConfigEntry.java
index 5943801dea..3deab1103c 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/config/ProjectConfigEntry.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/config/ProjectConfigEntry.java
@@ -17,6 +17,7 @@ package com.google.gerrit.server.config;
 import com.google.common.base.Function;
 import com.google.common.collect.Lists;
 import com.google.gerrit.extensions.annotations.ExtensionPoint;
+import com.google.gerrit.extensions.api.projects.ProjectInput.ConfigValue;
 import com.google.gerrit.extensions.events.GitReferenceUpdatedListener;
 import com.google.gerrit.extensions.registration.DynamicMap;
 import com.google.gerrit.extensions.registration.DynamicMap.Entry;
@@ -201,6 +202,18 @@ public class ProjectConfigEntry {
     return null;
   }
 
+  /**
+   * Called before the project config is updated. To modify the value before the
+   * project config is updated, override this method and return the modified
+   * value. Default implementation returns the same value.
+   *
+   * @param configValue the original configValue that was entered.
+   * @return the modified configValue.
+   */
+  public ConfigValue preUpdate(ConfigValue configValue) {
+    return configValue;
+  }
+
   /**
    * Called after a project config is updated.
    *
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/project/PutConfig.java b/gerrit-server/src/main/java/com/google/gerrit/server/project/PutConfig.java
index 27e7b1b75f..5185d3ae46 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/project/PutConfig.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/project/PutConfig.java
@@ -240,6 +240,8 @@ public class PutConfig implements RestModifyView<ProjectResource, Input> {
             if (!value.equals(oldValue)) {
               validateProjectConfigEntryIsEditable(projectConfigEntry,
                   projectState, e.getKey(), pluginName);
+              v.setValue(projectConfigEntry.preUpdate(v.getValue()));
+              value = v.getValue().value;
               try {
                 switch (projectConfigEntry.getType()) {
                   case BOOLEAN: