diff --git a/README.md b/README.md
index 671247b..82b012c 100644
--- a/README.md
+++ b/README.md
@@ -84,7 +84,7 @@ logs.)
 * `file`: an arbitrary file to attach to the report. Saved as-is to disk, and
   a link is added to the github issue. The filename must be in the format
   `name.ext`, where `name` contains only alphanumerics, `-` or `_`, and `ext`
-  is one of `jpg`, `png`, or `txt`.
+  is one of `jpg`, `png`, `txt` or `json`.
 
   Not supported for the JSON upload encoding.
 
diff --git a/changelog.d/74.misc b/changelog.d/74.misc
new file mode 100644
index 0000000..e57bda0
--- /dev/null
+++ b/changelog.d/74.misc
@@ -0,0 +1 @@
+Update README.md to include json as a valid extension for file uploads.