diff --git a/harbour/ChangeLog b/harbour/ChangeLog
index fa72373df6..4017661582 100644
--- a/harbour/ChangeLog
+++ b/harbour/ChangeLog
@@ -1,3 +1,8 @@
+19991016-00:10 EDT David G. Holm <dholm@jsd-llc.com>
+
+   * doc/gmake.txt
+     + Documented C_USR and -DHARBOUR_USE_<platform>_GTAPI were missing.
+
 19991016-00:00 EDT David G. Holm <dholm@jsd-llc.com>
 
    * source/rtl/set.c
diff --git a/harbour/doc/gmake.txt b/harbour/doc/gmake.txt
index 5857d302d3..53362a563b 100644
--- a/harbour/doc/gmake.txt
+++ b/harbour/doc/gmake.txt
@@ -137,10 +137,12 @@ your architecture and compiler.
 For gcc on Win95/WinNT with the Cygwin library:
   HB_ARCHITECTURE   win32
   HB_COMPILER       gcc
+  C_USR             -DHARBOUR_USE_WIN_GTAPI
 
 For gcc on Win95/WinNT with the Mingw32 library:
   HB_ARCHITECTURE   win32
   HB_COMPILER       mingw32
+  C_USR             -DHARBOUR_USE_WIN_GTAPI
 
 For MSVC on Win95/WinNT:
   Notes: You must create an empty unistd.h in the include directory.
@@ -169,14 +171,17 @@ For IBM Visual Age C++ on OS/2:
   Note: You must create an empty unistd.h in the IBMCPP\INCLUDE directory.
   HB_ARCHITECTURE   os2
   HB_COMPILER       icc
+  C_USR             -DHARBOUR_USE_OS2_GTAPI
 
 For Borland C++ 3.1
   HB_ARCHITECTURE   dos
   HB_COMPILER       bcc31
+  C_USR             -DHARBOUR_USE_DOS_GTAPI
 
 For DJGPP (GCC port for DOS)
   HB_ARCHITECTURE   dos
   HB_COMPILER       djgpp
+  C_USR             -DHARBOUR_USE_DOS_GTAPI
 
 For Watcom C/C++ 10.x (default Makefile creates DOS4G extender executables)
   HB_ARCHITECTURE   dos