diff --git a/packages/react-dom/src/server/DOMMarkupOperations.js b/packages/react-dom/src/server/DOMMarkupOperations.js
index 7306d9393be56..3cddbb493e07e 100644
--- a/packages/react-dom/src/server/DOMMarkupOperations.js
+++ b/packages/react-dom/src/server/DOMMarkupOperations.js
@@ -71,7 +71,12 @@ export function createMarkupForCustomAttribute(
   name: string,
   value: mixed,
 ): string {
-  if (!isAttributeNameSafe(name) || value == null) {
+  if (
+    !isAttributeNameSafe(name) ||
+    value == null ||
+    typeof value === 'function' ||
+    typeof value === 'symbol'
+  ) {
     return '';
   }
   return name + '=' + quoteAttributeValueForBrowser(value);
diff --git a/packages/react-dom/src/server/ReactDOMServerFormatConfig.js b/packages/react-dom/src/server/ReactDOMServerFormatConfig.js
index 2a034963f48af..62f6d3ca56550 100644
--- a/packages/react-dom/src/server/ReactDOMServerFormatConfig.js
+++ b/packages/react-dom/src/server/ReactDOMServerFormatConfig.js
@@ -1070,7 +1070,11 @@ function pushStartCustomElement(
           // Ignored. These are built-in to React on the client.
           break;
         default:
-          if (isAttributeNameSafe(propKey)) {
+          if (
+            isAttributeNameSafe(propKey) &&
+            typeof propValue !== 'function' &&
+            typeof propValue !== 'symbol'
+          ) {
             target.push(
               attributeSeparator,
               stringToChunk(propKey),