3 files changed, 18 insertions, 7 deletions
diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index b61ea5298e1e..61286ceac9e4 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -1249,8 +1249,7 @@ void DerivationGoal::inputsRealised()
         }
 
     /* Second, the input sources. */
-    for (auto & i : drv->inputSrcs)
-        worker.store.computeFSClosure(i, inputPaths);
+    worker.store.computeFSClosure(drv->inputSrcs, inputPaths);
 
     debug(format("added input paths %1%") % showPaths(inputPaths));
 
diff --git a/src/libstore/misc.cc b/src/libstore/misc.cc
index 0c2c49e5531f..9a88cdc317b6 100644
--- a/src/libstore/misc.cc
+++ b/src/libstore/misc.cc
@@ -8,7 +8,7 @@
 namespace nix {
 
 
-void Store::computeFSClosure(const Path & startPath,
+void Store::computeFSClosure(const PathSet & startPaths,
     PathSet & paths_, bool flipDirection, bool includeOutputs, bool includeDerivers)
 {
     struct State
@@ -85,7 +85,8 @@ void Store::computeFSClosure(const Path & startPath,
             });
     };
 
-    enqueue(startPath);
+    for (auto & startPath : startPaths)
+        enqueue(startPath);
 
     {
         auto state(state_.lock());
@@ -95,6 +96,13 @@ void Store::computeFSClosure(const Path & startPath,
 }
 
 
+void Store::computeFSClosure(const Path & startPath,
+    PathSet & paths_, bool flipDirection, bool includeOutputs, bool includeDerivers)
+{
+    computeFSClosure(PathSet{startPath}, paths_, flipDirection, includeOutputs, includeDerivers);
+}
+
+
 void Store::queryMissing(const PathSet & targets,
     PathSet & willBuild_, PathSet & willSubstitute_, PathSet & unknown_,
     unsigned long long & downloadSize_, unsigned long long & narSize_)
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index f6bbc9a84e18..2ea74d90e78e 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -477,15 +477,19 @@ public:
        ensurePath(). */
     Derivation derivationFromPath(const Path & drvPath);
 
-    /* Place in `paths' the set of all store paths in the file system
+    /* Place in `out' the set of all store paths in the file system
        closure of `storePath'; that is, all paths than can be directly
-       or indirectly reached from it.  `paths' is not cleared.  If
+       or indirectly reached from it.  `out' is not cleared.  If
        `flipDirection' is true, the set of paths that can reach
        `storePath' is returned; that is, the closures under the
        `referrers' relation instead of the `references' relation is
        returned. */
+    void computeFSClosure(const PathSet & paths,
+        PathSet & out, bool flipDirection = false,
+        bool includeOutputs = false, bool includeDerivers = false);
+
     void computeFSClosure(const Path & path,
-        PathSet & paths, bool flipDirection = false,
+        PathSet & out, bool flipDirection = false,
         bool includeOutputs = false, bool includeDerivers = false);
 
     /* Given a set of paths that are to be built, return the set of