3 files changed, 19 insertions, 0 deletions
diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index 1fc966951..8e5ab7594 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -2528,6 +2528,12 @@ SingleDrvOutputs LocalDerivationGoal::registerOutputs()
             [&](const DerivationOutput::CAFixed & dof) {
                 auto & wanted = dof.ca.hash;
 
+                // Replace the output by a fresh copy of itself to make sure
+                // that there's no stale file descriptor pointing to it
+                Path tmpOutput = actualPath + ".tmp";
+                movePath(actualPath, tmpOutput);
+                copyFile(tmpOutput, actualPath, true);
+
                 auto newInfo0 = newInfoFromCA(DerivationOutput::CAFloating {
                     .method = dof.ca.method,
                     .hashType = wanted.type,
diff --git a/src/libutil/filesystem.cc b/src/libutil/filesystem.cc
index 11cc0c0e7..2a7787c0e 100644
--- a/src/libutil/filesystem.cc
+++ b/src/libutil/filesystem.cc
@@ -133,6 +133,12 @@ void copy(const fs::directory_entry & from, const fs::path & to, bool andDelete)
     }
 }
 
+
+void copyFile(const Path & oldPath, const Path & newPath, bool andDelete)
+{
+    return copy(fs::directory_entry(fs::path(oldPath)), fs::path(newPath), andDelete);
+}
+
 void renameFile(const Path & oldName, const Path & newName)
 {
     fs::rename(oldName, newName);
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index bcee42327..acd77ee33 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -275,6 +275,13 @@ void renameFile(const Path & src, const Path & dst);
  */
 void moveFile(const Path & src, const Path & dst);
 
+/**
+ * Recursively copy the content of `oldPath` to `newPath`. If `andDelete` is
+ * `true`, then also remove `oldPath` (making this equivalent to `moveFile`, but
+ * with the guaranty that the destination will be “fresh”, with no stale inode
+ * or file descriptor pointing to it).
+ */
+void copyFile(const Path & oldPath, const Path & newPath, bool andDelete);
 
 /**
  * Wrappers arount read()/write() that read/write exactly the