diff --git a/src/libexpr/flake/flake.cc b/src/libexpr/flake/flake.cc
index c1a099613..6893f157e 100644
--- a/src/libexpr/flake/flake.cc
+++ b/src/libexpr/flake/flake.cc
@@ -710,8 +710,9 @@ Fingerprint LockedFlake::getFingerprint() const
     // and we haven't changed it, then it's sufficient to use
     // flake.sourceInfo.storePath for the fingerprint.
     return hashString(htSHA256,
-        fmt("%s;%d;%d;%s",
+        fmt("%s;%s;%d;%d;%s",
             flake.sourceInfo->storePath.to_string(),
+            flake.lockedRef.subdir,
             flake.lockedRef.input.getRevCount().value_or(0),
             flake.lockedRef.input.getLastModified().value_or(0),
             lockFile));