Fix file extensions table formatting
diff --git a/source/documentation/io/__index.md b/source/documentation/io/__index.md
index e2a1b80..6214bdb 100644
--- a/source/documentation/io/__index.md
+++ b/source/documentation/io/__index.md
@@ -58,7 +58,7 @@
 | `.jsonld` | JSON-LD      |
 | `.trdf`   | RDF Thrift   |
 | `.rt`     | RDF Thrift   |
-| `.rpb     | RDF Protobuf |
+| `.rpb`    | RDF Protobuf |
 | `.pbrdf`  | RDF Protobuf |
 | `.rj`     | RDF/JSON     |
 | `.trix`   | TriX         |