diff --git a/harbour/ChangeLog b/harbour/ChangeLog
index 1bf87c1d7c..b62e9e09f2 100644
--- a/harbour/ChangeLog
+++ b/harbour/ChangeLog
@@ -17,6 +17,10 @@
    past entries belonging to author(s): Viktor Szakats.
 */
 
+2009-06-22 15:23 UTC+0200 Viktor Szakats (harbour.01 syenar.hu)
+  * INSTALL
+    + Documented HB_BUILD_MODE envvar.
+
 2009-06-22 15:03 UTC+0200 Viktor Szakats (harbour.01 syenar.hu)
   * config/hpux/gcc.cf
   * config/sunos/gcc.cf
diff --git a/harbour/INSTALL b/harbour/INSTALL
index f7edf21cc4..93cd2ff61f 100644
--- a/harbour/INSTALL
+++ b/harbour/INSTALL
@@ -252,6 +252,7 @@ OPTIONS AVAILABLE WHEN BUILDING HARBOUR
                                pass them to make_gnu.bat.
    - HB_BUILD_DEBUG=yes        Create a debug build.
    - HB_BUILD_OPTIM=no         Disable C compiler optimizations.
+   - HB_BUILD_MODE=yes|no      Changes default build mode to C++ or C.
    - HB_CONTRIBLIBS=no         Don't build any contrib libraries.
    - HB_CONTRIBLIBS=[<list>]   Build space separated <list> of contrib
                                libraries. Build all if left empty.