diff --git a/src/coreclr/gc/gc.cpp b/src/coreclr/gc/gc.cpp
index 4cc0ff0fc19473..6aee205096ba7e 100644
--- a/src/coreclr/gc/gc.cpp
+++ b/src/coreclr/gc/gc.cpp
@@ -24170,12 +24170,17 @@ BOOL ref_p (uint8_t* r)
     return (straight_ref_p (r) || partial_object_p (r));
 }
 
-mark_queue_t::mark_queue_t() : curr_slot_index(0)
+mark_queue_t::mark_queue_t()
+#ifdef MARK_PHASE_PREFETCH
+    : curr_slot_index(0)
+#endif //MARK_PHASE_PREFETCH
 {
+#ifdef MARK_PHASE_PREFETCH
     for (size_t i = 0; i < slot_count; i++)
     {
         slot_table[i] = nullptr;
     }
+#endif //MARK_PHASE_PREFETCH
 }
 
 // place an object in the mark queue
@@ -24185,6 +24190,7 @@ mark_queue_t::mark_queue_t() : curr_slot_index(0)
 FORCEINLINE
 uint8_t *mark_queue_t::queue_mark(uint8_t *o)
 {
+#ifdef MARK_PHASE_PREFETCH
     Prefetch (o);
 
     // while the prefetch is taking effect, park our object in the queue
@@ -24197,6 +24203,9 @@ uint8_t *mark_queue_t::queue_mark(uint8_t *o)
     curr_slot_index = (slot_index + 1) % slot_count;
     if (old_o == nullptr)
         return nullptr;
+#else //MARK_PHASE_PREFETCH
+    uint8_t* old_o = o;
+#endif //MARK_PHASE_PREFETCH
 
     // this causes us to access the method table pointer of the old object
     BOOL already_marked = marked (old_o);
@@ -24248,6 +24257,7 @@ uint8_t *mark_queue_t::queue_mark(uint8_t *o, int condemned_gen)
 // returns nullptr if there is no such object
 uint8_t* mark_queue_t::get_next_marked()
 {
+#ifdef MARK_PHASE_PREFETCH
     size_t slot_index = curr_slot_index;
     size_t empty_slot_count = 0;
     while (empty_slot_count < slot_count)
@@ -24267,15 +24277,18 @@ uint8_t* mark_queue_t::get_next_marked()
         }
         empty_slot_count++;
     }
+#endif //MARK_PHASE_PREFETCH
     return nullptr;
 }
 
 void mark_queue_t::verify_empty()
 {
+#ifdef MARK_PHASE_PREFETCH
     for (size_t slot_index = 0; slot_index < slot_count; slot_index++)
     {
         assert(slot_table[slot_index] == nullptr);
     }
+#endif //MARK_PHASE_PREFETCH
 }
 
 void gc_heap::mark_object_simple1 (uint8_t* oo, uint8_t* start THREAD_NUMBER_DCL)
diff --git a/src/coreclr/gc/gcpriv.h b/src/coreclr/gc/gcpriv.h
index 54f4664660e027..599a5b86908492 100644
--- a/src/coreclr/gc/gcpriv.h
+++ b/src/coreclr/gc/gcpriv.h
@@ -62,6 +62,7 @@ inline void FATAL_GC_ERROR()
 // + creates some ro segs
 // We can add more mechanisms here.
 //#define STRESS_REGIONS
+#define MARK_PHASE_PREFETCH
 #endif //USE_REGIONS
 
 // FEATURE_STRUCTALIGN was added by Midori. In CLR we are not interested
@@ -1222,9 +1223,11 @@ enum bookkeeping_element
 
 class mark_queue_t
 {
+#ifdef MARK_PHASE_PREFETCH
     static const size_t slot_count = 16;
     uint8_t* slot_table[slot_count];
     size_t curr_slot_index;
+#endif //MARK_PHASE_PREFETCH
 
 public:
     mark_queue_t();