diff --git a/src/promnesia/sources/filetypes.py b/src/promnesia/sources/filetypes.py
index 150519ad..76e1de07 100644
--- a/src/promnesia/sources/filetypes.py
+++ b/src/promnesia/sources/filetypes.py
@@ -63,6 +63,7 @@ def type2idx(t: str) -> Optional[Ex]:
     'text/troff',
     'text/x-asm',
     'text/x-objective-c',
+    'text/x-lisp',
 
     # these didn't have a mime type, or were mistyped?
     'css',