diff --git a/src/share/vm/memory/collectorPolicy.cpp b/src/share/vm/memory/collectorPolicy.cpp
index 61efdd80f7d38c90647bf8d5bc79e6c2e0b67470..7ad2bebaf4232c74e8456f95ec131fcf68ec3934 100644
--- a/src/share/vm/memory/collectorPolicy.cpp
+++ b/src/share/vm/memory/collectorPolicy.cpp
@@ -265,8 +265,6 @@ void TwoGenerationCollectorPolicy::initialize_flags() {
   MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
 
   always_do_update_barrier = UseConcMarkSweepGC;
-  BlockOffsetArrayUseUnallocatedBlock =
-      BlockOffsetArrayUseUnallocatedBlock || ParallelGCThreads > 0;
 
   // Check validity of heap flags
   assert(OldSize     % min_alignment() == 0, "old space alignment");
diff --git a/src/share/vm/runtime/globals.hpp b/src/share/vm/runtime/globals.hpp
index c16f8866056a598d7f9e6eb24b445de930641b51..59f8fb95a2579a832d77c88229b4a945d80b0fc4 100644
--- a/src/share/vm/runtime/globals.hpp
+++ b/src/share/vm/runtime/globals.hpp
@@ -1824,7 +1824,7 @@ class CommandLineFlags {
   develop(bool, VerifyBlockOffsetArray, false,                              \
           "Do (expensive!) block offset array verification")                \
                                                                             \
-  product(bool, BlockOffsetArrayUseUnallocatedBlock, false,                 \
+  diagnostic(bool, BlockOffsetArrayUseUnallocatedBlock, false,              \
           "Maintain _unallocated_block in BlockOffsetArray"                 \
           " (currently applicable only to CMS collector)")                  \
                                                                             \