diff --git a/internal/handlers/auth.go b/internal/handlers/auth.go
index 171b900..a0ad493 100644
--- a/internal/handlers/auth.go
+++ b/internal/handlers/auth.go
@@ -18,9 +18,9 @@ import (
 	"sneak.berlin/go/pixa/internal/templates"
 )
 
-// errInvalidFormField reports a generator form field, or the q parameter of
-// /v1/image/, whose value is non-numeric or out of range. The offending field
-// name is wrapped in so the response can name it.
+// errInvalidFormField reports a generator form field, or the q or exp
+// parameter of /v1/image/, whose value is non-numeric or out of range. The
+// offending field name is wrapped in so the response can name it.
 var errInvalidFormField = errors.New("invalid")
 
 // Bounds for the generator's quality and ttl fields; the quality bounds also