diff --git a/dist/index.js b/dist/index.js
index 81db06c..a374c0e 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -142,7 +142,7 @@ function run() {
                 core.info(tag);
             }
             core.endGroup();
-            core.setOutput('tags', tags.join(inputs.sepTags));
+            core.setOutput('tags', tags.join(inputs.sepTags).toLowerCase());
             const labels = meta.labels();
             core.startGroup(`Docker labels`);
             for (let label of labels) {
diff --git a/src/main.ts b/src/main.ts
index d61b4fc..e17efbd 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -39,7 +39,7 @@ async function run() {
       core.info(tag);
     }
     core.endGroup();
-    core.setOutput('tags', tags.join(inputs.sepTags));
+    core.setOutput('tags', tags.join(inputs.sepTags).toLowerCase());
 
     const labels: Array<string> = meta.labels();
     core.startGroup(`Docker labels`);