diff --git a/runtime/gc/collector/semi_space.cc b/runtime/gc/collector/semi_space.cc
index e82d533..6e31cb7 100644
--- a/runtime/gc/collector/semi_space.cc
+++ b/runtime/gc/collector/semi_space.cc
@@ -63,7 +63,6 @@
 namespace collector {
 
 static constexpr bool kProtectFromSpace = true;
-static constexpr bool kClearFromSpace = true;
 static constexpr bool kStoreStackTraces = false;
 static constexpr bool kUseBytesPromoted = true;
 static constexpr size_t kBytesPromotedThreshold = 4 * MB;
@@ -122,6 +121,7 @@
   // Do any pre GC verification.
   timings_.NewSplit("PreGcVerification");
   heap_->PreGcVerification(this);
+  CHECK(from_space_->CanMoveObjects()) << "Attempting to move from " << *from_space_;
   // Set the initial bitmap.
   to_space_live_bitmap_ = to_space_->GetLiveBitmap();
 }
@@ -182,9 +182,6 @@
   Locks::mutator_lock_->AssertExclusiveHeld(self_);
 
   TimingLogger::ScopedSplit split("MarkingPhase", &timings_);
-  // Need to do this with mutators paused so that somebody doesn't accidentally allocate into the
-  // wrong space.
-  heap_->SwapSemiSpaces();
   if (generational_) {
     // If last_gc_to_space_end_ is out of the bounds of the from-space
     // (the to-space from last GC), then point it to the beginning of
@@ -414,11 +411,7 @@
     TimingLogger::ScopedSplit split("UnBindBitmaps", &timings_);
     GetHeap()->UnBindBitmaps();
   }
-  if (kClearFromSpace) {
-    // Release the memory used by the from space.
-    from_space_->Clear();
-  }
-  from_space_->Reset();
+  from_space_->Clear();
   // Protect the from space.
   VLOG(heap) << "Protecting space " << *from_space_;
   if (kProtectFromSpace) {