diff --git a/resources/fieldsets/gist_block.yaml b/resources/fieldsets/gist_block.yaml
index a538c10..065c86c 100644
--- a/resources/fieldsets/gist_block.yaml
+++ b/resources/fieldsets/gist_block.yaml
@@ -16,7 +16,7 @@ fields:
     localizable: false
     display: Code
   extension:
-    character_limit: 3
+    character_limit: 4
     type: text
     localizable: false
     display: File Extension