diff --git a/src/m/ibmrs6000.h b/src/m/ibmrs6000.h
index ad5b272fbc6..46e8290c268 100644
--- a/src/m/ibmrs6000.h
+++ b/src/m/ibmrs6000.h
@@ -122,10 +122,10 @@ the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
 #define C_SWITCH_MACHINE -D_BSD
 
 #ifdef AIX3_2
-/* -lpthread seems to be necessary for Xlib in X11R6, and should be harmless
+/* -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_LIBPTHREAD
-#define LIBS_MACHINE -lrts -lIM -liconv -lpthread
+#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