diff --git a/nix/libstore/local-store.cc b/nix/libstore/local-store.cc
index 347e8a7..80566ea 100644
--- a/nix/libstore/local-store.cc
+++ b/nix/libstore/local-store.cc
@@ -1391,7 +1391,7 @@ Path LocalStore::addToStoreFromDump(const string & dump, const string & name,
                 StringSource source(dump);
                 restorePath(dstPath, source);
             } else
-                writeFile(dstPath, dump);
+                writeFileAtomically(dstPath, dump);
 
             canonicalisePathMetaData(dstPath, -1);
 
diff --git a/nix/libutil/util.cc b/nix/libutil/util.cc
index c077544..e33824b 100644
--- a/nix/libutil/util.cc
+++ b/nix/libutil/util.cc
@@ -272,6 +272,22 @@ void writeFile(const Path & path, const string & s)
     writeFull(fd, s);
 }
 
+void writeFileAtomically(const Path & path, const string & s)
+{
+    auto tmpPath = path + ".tmp";
+    AutoCloseFD fd = open(tmpPath.c_str(), O_WRONLY | O_TRUNC | O_CREAT, 0666);
+    if (fd == -1)
+        throw SysError(format("opening file '%1%'") % tmpPath);
+    writeFull(fd, s);
+#if _POSIX_SYNCHRONIZED_IO > 0
+    if (fdatasync(fd) != 0)
+        throw SysError(format("flushing file '%1%'") % tmpPath);
+#endif
+    fd.close();
+    if (rename(tmpPath.c_str(), path.c_str()) != 0)
+        throw SysError(format("renaming '%1%' to '%2'") % tmpPath % path);
+}
+
 
 string readLine(int fd)
 {
diff --git a/nix/libutil/util.hh b/nix/libutil/util.hh
index e84d64d..829f90b 100644
--- a/nix/libutil/util.hh
+++ b/nix/libutil/util.hh
@@ -86,6 +86,9 @@ string readFile(const Path & path, bool drain = false);
 /* Write a string to a file. */
 void writeFile(const Path & path, const string & s);
 
+/* Same, but do it atomically.  */
+void writeFileAtomically(const Path & path, const string & s);
+
 /* Read a line from a file descriptor. */
 string readLine(int fd);