diff --git a/sstables/compaction_manager.cc b/sstables/compaction_manager.cc
index 83031e698d..dffaad1bb5 100644
--- a/sstables/compaction_manager.cc
+++ b/sstables/compaction_manager.cc
@@ -124,6 +124,19 @@ std::vector<sstables::shared_sstable> compaction_manager::get_candidates(const c
     return candidates;
 }
 
+void compaction_manager::register_compacting_sstables(const std::vector<sstables::shared_sstable>& sstables) {
+    for (auto& sst : sstables) {
+        _compacting_sstables.insert(sst);
+    }
+}
+
+void compaction_manager::deregister_compacting_sstables(const std::vector<sstables::shared_sstable>& sstables) {
+    // Remove compacted sstables from the set of compacting sstables.
+    for (auto& sst : sstables) {
+        _compacting_sstables.erase(sst);
+    }
+}
+
 lw_shared_ptr<compaction_manager::task> compaction_manager::task_start(column_family* cf, bool cleanup) {
     // NOTE: Compaction code runs in parallel to the rest of the system.
     // When it's time to shutdown, we need to prevent any new compaction
@@ -148,18 +161,12 @@ lw_shared_ptr<compaction_manager::task> compaction_manager::task_start(column_fa
         // Created to erase sstables from _compacting_sstables after compaction finishes.
         std::vector<sstables::shared_sstable> sstables_to_compact;
         int weight = -1;
-        auto keep_track_of_compacting_sstables = [this, &sstables_to_compact, &descriptor] {
-            sstables_to_compact.reserve(descriptor.sstables.size());
-            for (auto& sst : descriptor.sstables) {
-                sstables_to_compact.push_back(sst);
-                _compacting_sstables.insert(sst);
-            }
-        };
 
         future<> operation = make_ready_future<>();
         if (task->cleanup) {
             descriptor = sstables::compaction_descriptor(std::move(candidates));
-            keep_track_of_compacting_sstables();
+            sstables_to_compact = descriptor.sstables;
+            register_compacting_sstables(sstables_to_compact);
             operation = cf.cleanup_sstables(std::move(descriptor));
         } else {
             sstables::compaction_strategy cs = cf.get_compaction_strategy();
@@ -173,7 +180,8 @@ lw_shared_ptr<compaction_manager::task> compaction_manager::task_start(column_fa
                     descriptor.sstables.size(), weight, cf.schema()->ks_name(), cf.schema()->cf_name());
                 return make_ready_future<stop_iteration>(stop_iteration::yes);
             }
-            keep_track_of_compacting_sstables();
+            sstables_to_compact = descriptor.sstables;
+            register_compacting_sstables(sstables_to_compact);
             cmlog.debug("Accepted compaction job ({} sstable(s)) of weight {} for {}.{}",
                 descriptor.sstables.size(), weight, cf.schema()->ks_name(), cf.schema()->cf_name());
             operation = cf.run_compaction(std::move(descriptor));
@@ -186,10 +194,7 @@ lw_shared_ptr<compaction_manager::task> compaction_manager::task_start(column_fa
             task->compaction_retry.reset();
             return make_ready_future<>();
         }).then_wrapped([this, task, weight, sstables_to_compact = std::move(sstables_to_compact)] (future<> f) {
-            // Remove compacted sstables from the set of compacting sstables.
-            for (auto& sst : sstables_to_compact) {
-                _compacting_sstables.erase(sst);
-            }
+            deregister_compacting_sstables(sstables_to_compact);
             if (weight != -1) {
                 deregister_weight(task->compacting_cf, weight);
             }
diff --git a/sstables/compaction_manager.hh b/sstables/compaction_manager.hh
index bcec997c36..3be09fc70a 100644
--- a/sstables/compaction_manager.hh
+++ b/sstables/compaction_manager.hh
@@ -93,6 +93,9 @@ private:
 
     // Get candidates for compaction strategy, which are all sstables but the ones being compacted.
     std::vector<sstables::shared_sstable> get_candidates(const column_family& cf);
+
+    void register_compacting_sstables(const std::vector<sstables::shared_sstable>& sstables);
+    void deregister_compacting_sstables(const std::vector<sstables::shared_sstable>& sstables);
 public:
     compaction_manager();
     ~compaction_manager();