diff --git a/src/dav.rs b/src/dav.rs
index cb6a8b1..d89f1d4 100644
--- a/src/dav.rs
+++ b/src/dav.rs
@@ -212,10 +212,11 @@ pub fn multistatus(body: &[u8]) -> Result<Vec<Found>, ErrorCode> {
 /// Some servers, WsgiDAV among them, list `getetag` bare while their `ETag`
 /// header quotes the same tag, so a revision read from a listing and one
 /// returned by a write would differ for the same bytes. Quoting a bare tag
-/// gives every revision one spelling, and `If-Match` accepts that form.
+/// gives every revision one spelling, and `If-Match` accepts that form. A tag
+/// that is already quoted, weak or strong, is kept as it is.
 pub fn etag(value: &str) -> String {
   let value = value.trim();
-  if value.starts_with('"') || value.starts_with("W/") {
+  if value.starts_with('"') || value.starts_with("W/\"") {
     value.to_owned()
   } else {
     format!("\"{value}\"")
@@ -435,5 +436,6 @@ mod tests {
     assert_eq!(etag("1996000-1790356720-264"), "\"1996000-1790356720-264\"");
     assert_eq!(etag(" \"v1\" "), "\"v1\"");
     assert_eq!(etag("W/\"v1\""), "W/\"v1\"");
+    assert_eq!(etag("W/v1"), "\"W/v1\"");
   }
 }