diff --git a/README.md b/README.md
index 82b012c..10b1f61 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`, `txt` or `json`.
+  is one of `jpg`, `png`, `txt`, `json`, `txt.gz` or `json.gz`.
 
   Not supported for the JSON upload encoding.
 
diff --git a/changelog.d/75.feature b/changelog.d/75.feature
new file mode 100644
index 0000000..b13ca06
--- /dev/null
+++ b/changelog.d/75.feature
@@ -0,0 +1 @@
+Allow gzipped json & txt files to be uploaded as attachments to rageshakes.
diff --git a/logserver.go b/logserver.go
index 235fcdd..70015ef 100644
--- a/logserver.go
+++ b/logserver.go
@@ -104,8 +104,12 @@ func serveFile(w http.ResponseWriter, r *http.Request, path string) {
 //
 // Unlike mime.TypeByExtension, the results are limited to a set of types which
 // should be safe to serve to a browser without introducing XSS vulnerabilities.
+//
+// We handle all of the extensions we allow on files uploaded as attachments to a rageshake,
+// plus 'log' which we do not allow as an attachment, but is used as the extension when serving
+// the logs submitted as `logs` or `compressed-log`.
 func extensionToMimeType(path string) string {
-	if strings.HasSuffix(path, ".txt") {
+	if strings.HasSuffix(path, ".txt") || strings.HasSuffix(path, ".log") {
 		// anyone uploading text in anything other than utf-8 needs to be
 		// re-educated.
 		return "text/plain; charset=utf-8"
@@ -236,7 +240,13 @@ func addToArchive(targz *tar.Writer, dfilename string, filename string) error {
 }
 
 func serveGzippedFile(w http.ResponseWriter, r *http.Request, path string, size int64) {
-	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+	cType := "text/plain; charset=utf-8"
+	if strings.HasSuffix(path, ".gz") {
+		// Guess the mime type from the extension as we do in serveFile, but without
+		// the .gz header (in practice, either plain text or application/json).
+		cType = extensionToMimeType(path[:len(path)-len(".gz")])
+	}
+	w.Header().Set("Content-Type", cType)
 
 	acceptsGzip := false
 	splitRune := func(s rune) bool { return s == ' ' || s == '\t' || s == '\n' || s == ',' }
diff --git a/submit.go b/submit.go
index b733cdb..6e4b8f2 100644
--- a/submit.go
+++ b/submit.go
@@ -405,12 +405,13 @@ func formPartToPayload(field, data string, p *payload) {
 // * a limited set of extensions. We are careful to limit the content-types
 //   we will serve the files with, but somebody might accidentally point an
 //   Apache or nginx at the upload directory, which would serve js files as
-//   application/javascript and open XSS vulnerabilities.
+//   application/javascript and open XSS vulnerabilities. We also allow gzipped
+//   text and json on the same basis (there's really no sense allowing gzipped images).
 //
 // * no silly characters (/, ctrl chars, etc)
 //
 // * nothing starting with '.'
-var filenameRegexp = regexp.MustCompile(`^[a-zA-Z0-9_-]+\.(jpg|png|txt|json)$`)
+var filenameRegexp = regexp.MustCompile(`^[a-zA-Z0-9_-]+\.(jpg|png|txt|json|txt\.gz|json\.gz)$`)
 
 // saveFormPart saves a file upload to the report directory.
 //