diff --git a/gtsam_unstable/nonlinear/ConcurrentBatchFilter.cpp b/gtsam_unstable/nonlinear/ConcurrentBatchFilter.cpp
index 21ae50347..3bb9c7e44 100644
--- a/gtsam_unstable/nonlinear/ConcurrentBatchFilter.cpp
+++ b/gtsam_unstable/nonlinear/ConcurrentBatchFilter.cpp
@@ -537,9 +537,7 @@ void ConcurrentBatchFilter::moveSeparator(const FastList<Key>& keysToMove) {
   VariableIndex variableIndex(factors_);
   BOOST_FOREACH(Key key, keysToMove) {
     const FastList<size_t>& slots = variableIndex[key];
-    BOOST_FOREACH(size_t slot, slots) {
-      removedFactorSlots.insert(removedFactorSlots.end(), slots.begin(), slots.end());
-    }
+    removedFactorSlots.insert(removedFactorSlots.end(), slots.begin(), slots.end());
   }
 
   // Sort and remove duplicates
@@ -658,4 +656,4 @@ void ConcurrentBatchFilter::moveSeparator(const FastList<Key>& keysToMove) {
 }
 
 /* ************************************************************************* */
-}/// namespace gtsam
\ No newline at end of file
+}/// namespace gtsam