diff --git a/doc/system/changes.adoc b/doc/system/changes.adoc
index dcfd9fa..1c03db3 100644
--- a/doc/system/changes.adoc
+++ b/doc/system/changes.adoc
@@ -38,7 +38,7 @@ In addition to enabling use in constant expressions (and `constexpr`
 functions), this significantly improves the quality of the generated code.
 
 As a result of this change, however, now using Boost.System from {cpp}14
-or {cpp}17 code requires that the library is also built with {cpp}14 or
+or {cpp}17 code requires that the library be also built with {cpp}14 or
 above. This is the default on GCC 6 and newer, but not on GCC 5 or Clang.
 One can build Boost for {cpp}14 by passing the `cxxstd=14` option to `b2`.
 
diff --git a/doc/system/rationale.adoc b/doc/system/rationale.adoc
index 49096c9..fe65421 100644
--- a/doc/system/rationale.adoc
+++ b/doc/system/rationale.adoc
@@ -12,7 +12,7 @@ http://www.boost.org/LICENSE_1_0.txt
 :idprefix: rationale_
 
 `error_code` and `error_condition` are designed as value types so
-they can be copied without slicing and do not requiring heap allocation, but
+they can be copied without slicing and do not require heap allocation, but
 still have polymorphic behavior based on the error category. This is achieved
 by abstract base class `error_category` supplying the polymorphic behavior,
 and `error_code` and `error_condition` containing a pointer to an object of a