diff --git a/config/jsdoc/info/publish.js b/config/jsdoc/info/publish.js
index 5d0eca556b..12e409027c 100644
--- a/config/jsdoc/info/publish.js
+++ b/config/jsdoc/info/publish.js
@@ -103,11 +103,19 @@ exports.publish = function(data, opts) {
           if (typeof param.optional == 'boolean') {
             paramInfo.optional = param.optional;
           }
+          if (typeof param.nullable == 'boolean') {
+            paramInfo.nullable = param.nullable;
+          }
         });
         symbol.params = params;
       }
       if (doc.returns) {
-        symbol.returns = getTypes(doc.returns[0].type.names);
+        symbol.returns = {
+          types: getTypes(doc.returns[0].type.names)
+        };
+        if (typeof doc.returns[0].nullable == 'boolean') {
+          symbol.returns.nullable = doc.returns[0].nullable;
+        }
       }
       if (doc.tags) {
         doc.tags.every(function(tag) {
diff --git a/tasks/generate-externs.js b/tasks/generate-externs.js
index c93472d5dd..dd9c61e286 100644
--- a/tasks/generate-externs.js
+++ b/tasks/generate-externs.js
@@ -105,12 +105,14 @@ function generateExterns(typedefs, symbols, externs) {
         lines.push(' * @param {' +
             (param.variable ? '...' : '') +
             noGoogTypes(param.types).join('|') +
-            (param.optional ? '=' : '') +
+            (param.optional ? '=' : '') + (param.nullable ? '!' : '') +
             '} ' + param.name);
       });
     }
     if (symbol.returns) {
-      lines.push(' * @return {' + noGoogTypes(symbol.returns).join('|') + '}');
+      lines.push(' * @return {' +
+          (symbol.returns.nullable ? '!' : '') +
+          noGoogTypes(symbol.returns.types).join('|') + '}');
     }
     if (symbol.template) {
       lines.push(' * @template ' + symbol.template);