diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 03aaeca1af5..4ea9dbfc18a 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,8 @@
 2018-11-13  Jonathan Wakely  <jwakely@redhat.com>
 
+	* src/c++17/memory_resource.cc (select_num_pools): Fix off-by-one
+	error when block_size is equal to one of the values in the array.
+
 	* src/c++17/memory_resource.cc (_Pool::deallocate): Restore
 	attributes to parameters that are only used in assertions.
 
diff --git a/libstdc++-v3/src/c++17/memory_resource.cc b/libstdc++-v3/src/c++17/memory_resource.cc
index cb91e5147ce..605bdd53950 100644
--- a/libstdc++-v3/src/c++17/memory_resource.cc
+++ b/libstdc++-v3/src/c++17/memory_resource.cc
@@ -892,7 +892,7 @@ namespace pmr
     auto p = std::lower_bound(std::begin(pool_sizes), std::end(pool_sizes),
 			      opts.largest_required_pool_block);
     const int n = p - std::begin(pool_sizes);
-    if (p == std::end(pool_sizes) || *p == opts.largest_required_pool_block)
+    if (p == std::end(pool_sizes))
       return n;
     return n + 1;
   }