diff --git a/src/hotspot/share/gc/g1/g1ConcurrentMark.hpp b/src/hotspot/share/gc/g1/g1ConcurrentMark.hpp
index 441e4943958..3d9693bed10 100644
--- a/src/hotspot/share/gc/g1/g1ConcurrentMark.hpp
+++ b/src/hotspot/share/gc/g1/g1ConcurrentMark.hpp
@@ -561,7 +561,7 @@ public:
   // Sets the internal top_at_region_start for the given region to current top of the region.
   inline void update_top_at_rebuild_start(HeapRegion* r);
   // TARS for the given region during remembered set rebuilding.
-  inline HeapWord* top_at_rebuild_start(uint region) const;
+  inline HeapWord* top_at_rebuild_start(HeapRegion* r) const;
 
   // Clear statistics gathered during the concurrent cycle for the given region after
   // it has been reclaimed.
diff --git a/src/hotspot/share/gc/g1/g1ConcurrentMark.inline.hpp b/src/hotspot/share/gc/g1/g1ConcurrentMark.inline.hpp
index 4e4e64ab797..4a05b86ae5a 100644
--- a/src/hotspot/share/gc/g1/g1ConcurrentMark.inline.hpp
+++ b/src/hotspot/share/gc/g1/g1ConcurrentMark.inline.hpp
@@ -184,9 +184,8 @@ inline size_t G1CMTask::scan_objArray(objArrayOop obj, MemRegion mr) {
   return mr.word_size();
 }
 
-inline HeapWord* G1ConcurrentMark::top_at_rebuild_start(uint region) const {
-  assert(region < _g1h->max_reserved_regions(), "Tried to access TARS for region %u out of bounds", region);
-  return _top_at_rebuild_starts[region];
+inline HeapWord* G1ConcurrentMark::top_at_rebuild_start(HeapRegion* r) const {
+  return _top_at_rebuild_starts[r->hrm_index()];
 }
 
 inline void G1ConcurrentMark::update_top_at_rebuild_start(HeapRegion* r) {
diff --git a/src/hotspot/share/gc/g1/g1ConcurrentRebuildAndScrub.cpp b/src/hotspot/share/gc/g1/g1ConcurrentRebuildAndScrub.cpp
index ee16c42626c..74e242a0f3f 100644
--- a/src/hotspot/share/gc/g1/g1ConcurrentRebuildAndScrub.cpp
+++ b/src/hotspot/share/gc/g1/g1ConcurrentRebuildAndScrub.cpp
@@ -105,7 +105,7 @@ class G1RebuildRSAndScrubTask : public WorkerTask {
     //  - been allocated after rebuild start, or
     //  - been reclaimed by a collection.
     bool should_rebuild_or_scrub(HeapRegion* hr) const {
-      return _cm->top_at_rebuild_start(hr->hrm_index()) != nullptr;
+      return _cm->top_at_rebuild_start(hr) != nullptr;
     }
 
     // Helper used by both humongous objects and when chunking an object larger than the
@@ -229,7 +229,7 @@ class G1RebuildRSAndScrubTask : public WorkerTask {
       assert(should_rebuild_or_scrub(hr), "must be");
 
       log_trace(gc, marking)("Scrub and rebuild region: " HR_FORMAT " pb: " PTR_FORMAT " TARS: " PTR_FORMAT " TAMS: " PTR_FORMAT,
-                             HR_FORMAT_PARAMS(hr), p2i(pb), p2i(_cm->top_at_rebuild_start(hr->hrm_index())), p2i(hr->top_at_mark_start()));
+                             HR_FORMAT_PARAMS(hr), p2i(pb), p2i(_cm->top_at_rebuild_start(hr)), p2i(hr->top_at_mark_start()));
 
       if (scan_and_scrub_to_pb(hr, hr->bottom(), pb)) {
         log_trace(gc, marking)("Scan and scrub aborted for region: %u", hr->hrm_index());
@@ -246,7 +246,7 @@ class G1RebuildRSAndScrubTask : public WorkerTask {
       hr->note_end_of_scrubbing();
 
       // Rebuild from TAMS (= parsable_bottom) to TARS.
-      if (scan_from_pb_to_tars(hr, pb, _cm->top_at_rebuild_start(hr->hrm_index()))) {
+      if (scan_from_pb_to_tars(hr, pb, _cm->top_at_rebuild_start(hr))) {
         log_trace(gc, marking)("Rebuild aborted for region: %u (%s)", hr->hrm_index(), hr->get_short_type_str());
         return true;
       }
@@ -272,7 +272,7 @@ class G1RebuildRSAndScrubTask : public WorkerTask {
              "Humongous object not live");
 
       log_trace(gc, marking)("Rebuild for humongous region: " HR_FORMAT " pb: " PTR_FORMAT " TARS: " PTR_FORMAT,
-                              HR_FORMAT_PARAMS(hr), p2i(pb), p2i(_cm->top_at_rebuild_start(hr->hrm_index())));
+                              HR_FORMAT_PARAMS(hr), p2i(pb), p2i(_cm->top_at_rebuild_start(hr)));
 
       // Scan the humongous object in chunks from bottom to top to rebuild remembered sets.
       HeapWord* humongous_end = hr->humongous_start_region()->bottom() + humongous->size();