diff --git a/lib/reporter.js b/lib/reporter.js
index d8e488e..8768280 100644
--- a/lib/reporter.js
+++ b/lib/reporter.js
@@ -42,6 +42,10 @@ var CoverageReporter = function(rootConfig, helper, logger) {
   var sourceCache = globalSourceCache.getByBasePath(basePath);
   var includeAllSources = config.includeAllSources === true;
 
+  if (config.watermarks) {
+    config.watermarks = helper.merge({}, istanbul.config.defaultConfig().reporting.watermarks, config.watermarks);
+  }
+
   if (!helper.isDefined(reporters)) {
     reporters = [config];
   }