diff --git a/jam/jam.h b/jam/jam.h
index 6ce522a..866f920 100644
--- a/jam/jam.h
+++ b/jam/jam.h
@@ -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) && \