diff --git a/README.md b/README.md
index 65d9064..6bac5c6 100644
--- a/README.md
+++ b/README.md
@@ -156,6 +156,16 @@ You can disable new lines in the log output by setting the environment variable
 docker run -e LOG_WITHOUT_NEWLINE=true -p 8080:8080 -p 8443:8443 --rm -t mendhak/http-https-echo:31
 ```
 
+## Log to standard error
+
+By default the log output is always sent to standard out. If you want to vary the log output format you can set `LOG_TO_STANDARD_ERROR` which combined with `x-set-response-status-code` will log anything with a status code between 400 and 599, to standard error.
+
+```bash
+docker run -e LOG_TO_STANDARD_ERROR=true -p 8080:8080 -p 8443:8443 --rm -t mendhak/http-https-echo:31
+
+curl -v -H "x-set-response-status-code: 401" http://localhost:8080/
+```
+
 ## Send an empty response
 
 You can disable the JSON output in the response by setting the environment variable `ECHO_BACK_TO_CLIENT`. For example,
diff --git a/index.js b/index.js
index 03391c1..d62d99e 100644
--- a/index.js
+++ b/index.js
@@ -131,11 +131,17 @@ app.all('*', (req, res) => {
     if (process.env.LOG_IGNORE_PATH != req.path) {
 
       let spacer = 4;
-      if(process.env.LOG_WITHOUT_NEWLINE){
+      if(process.env.LOG_WITHOUT_NEWLINE) {
         spacer = null;
       }
 
-      console.log(JSON.stringify(echo, null, spacer));
+      //Allow logging to standard error if the status code is a failure
+      let loggerFunction = console.log;
+      if (process.env.LOG_TO_STANDARD_ERROR === "true" && setResponseStatusCode >= 400 && setResponseStatusCode < 600) {
+        loggerFunction = console.error;
+      }
+
+      loggerFunction(JSON.stringify(echo, null, spacer));
     }
   });