diff --git a/src/ChangeLog b/src/ChangeLog
index 7242bd4c371..f0be1af84c4 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,11 @@
+2010-03-23  Dan Nicolaescu  <dann@ics.uci.edu>
+
+	Simplify LIBS_MACHINE definitions.
+	* m/hp800.h (LIBS_MACHINE): Remove, same as default.
+	* m/iris4d.h (LIBS_MACHINE): Likewise.
+	* m/ibmrs6000.h (LIBS_MACHINE): Rename to LIBS_SYSTEM and move ...
+	* s/aix4-2.h (LIBS_SYSTEM): ... here.
+
 2010-03-22  Dan Nicolaescu  <dann@ics.uci.edu>
 
 	Remove dead code dealing with POSIX_SIGNALS.
diff --git a/src/m/hp800.h b/src/m/hp800.h
index 5614141fe63..8acec110272 100644
--- a/src/m/hp800.h
+++ b/src/m/hp800.h
@@ -93,7 +93,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #define UNEXEC unexhp9k800.o
 
-#define LIBS_MACHINE
 #define LIBS_DEBUG
 
 /* Include the file bsdtty.h, since this machine has job control.  */
diff --git a/src/m/ibmrs6000.h b/src/m/ibmrs6000.h
index 8e1d76b7e12..a7d35cc8ab7 100644
--- a/src/m/ibmrs6000.h
+++ b/src/m/ibmrs6000.h
@@ -57,15 +57,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #define NLIST_STRUCT
 #endif
 
-/* -lpthreads seems to be necessary for Xlib in X11R6, and should be harmless
-   on older versions of X where it happens to exist.  */
-#ifdef HAVE_LIBPTHREADS
-#define LIBS_MACHINE -lrts -lIM -liconv -lpthreads
-#else
-/* IBM's X11R5 use -lIM and -liconv in AIX 3.2.2.  */
-#define LIBS_MACHINE -lrts -lIM -liconv
-#endif
-
 #undef ADDR_CORRECT
 #define ADDR_CORRECT(x) ((int)(x))
 
diff --git a/src/m/iris4d.h b/src/m/iris4d.h
index 7c0ff78a069..06bffceb64c 100644
--- a/src/m/iris4d.h
+++ b/src/m/iris4d.h
@@ -53,8 +53,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #define DATA_START 0x10000000
 #define DATA_SEG_BITS	0x10000000
 
-#undef LIBS_MACHINE
-#define LIBS_MACHINE
 #define LIBS_DEBUG
 
 /* Use terminfo instead of termcap.  */
diff --git a/src/s/aix4-2.h b/src/s/aix4-2.h
index f4ffc606221..93869db6bca 100644
--- a/src/s/aix4-2.h
+++ b/src/s/aix4-2.h
@@ -95,6 +95,15 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #define LIB_STANDARD
 
+/* -lpthreads seems to be necessary for Xlib in X11R6, and should be harmless
+   on older versions of X where it happens to exist.  */
+#ifdef HAVE_LIBPTHREADS
+#define LIBS_SYSTEM -lrts -lIM -liconv -lpthreads
+#else
+/* IBM's X11R5 use -lIM and -liconv in AIX 3.2.2.  */
+#define LIBS_SYSTEM -lrts -lIM -liconv
+#endif
+
 /* Use terminfo instead of termcap.  */
 
 #define TERMINFO