diff -uNp jam.bak/Makefile jam/Makefile
--- jam.bak/Makefile	Mon Mar  5 20:32:08 2012
+++ jam/Makefile	Mon Mar  5 20:43:32 2012
@@ -1,7 +1,7 @@
 # Makefile for jam
 
 CC = cc
-CFLAGS = -O3
+CFLAGS = -O2
 EXENAME = ./jam0
 TARGET = -o $(EXENAME)
 HOST_SYSTEM=$(shell uname)
diff -uNp jam.bak/jam.h jam/jam.h
--- jam.bak/jam.h	Mon Mar  5 20:32:08 2012
+++ jam/jam.h	Mon Mar  5 20:43:21 2012
@@ -295,6 +295,12 @@
 # define OS_NETBSD
 # define NO_VFORK
 # endif
+# ifdef __OpenBSD__
+# define unix
+# define OSMINOR "OS=OPENBSD"
+# define OS_OPENBSD
+# define NO_VFORK
+# endif
 # ifdef __QNX__
 # ifdef __QNXNTO__
 # define OSMINOR "OS=QNXNTO"
@@ -391,6 +397,7 @@
 
 # if !defined(OS_BSDI) && \
      !defined(OS_FREEBSD) && \
+     !defined(OS_OPENBSD) && \
      !defined(OS_NEXT) && \
      !defined(OS_MACHTEN) && \
      !defined(OS_MACOSX) && \