Index: modcargo-crates/v8-0.99.0/v8/include/v8config.h
--- modcargo-crates/v8-0.99.0/v8/include/v8config.h.orig
+++ modcargo-crates/v8-0.99.0/v8/include/v8config.h
@@ -194,6 +194,7 @@ path. Add it with -I<path> to the command line
   && !defined(V8_TARGET_OS_IOS) \
   && !defined(V8_TARGET_OS_LINUX) \
   && !defined(V8_TARGET_OS_MACOS) \
+  && !defined(V8_TARGET_OS_OPENBSD) \
   && !defined(V8_TARGET_OS_WIN) \
   && !defined(V8_TARGET_OS_CHROMEOS)
 #  error No known target OS defined.
@@ -206,6 +207,7 @@ path. Add it with -I<path> to the command line
   || defined(V8_TARGET_OS_IOS) \
   || defined(V8_TARGET_OS_LINUX) \
   || defined(V8_TARGET_OS_MACOS) \
+  || defined(V8_TARGET_OS_OPENBSD) \
   || defined(V8_TARGET_OS_WIN) \
   || defined(V8_TARGET_OS_CHROMEOS)
 #  error A target OS is defined but V8_HAVE_TARGET_OS is unset.
@@ -226,6 +228,11 @@ path. Add it with -I<path> to the command line
 
 #ifdef V8_OS_LINUX
 # define V8_TARGET_OS_LINUX
+#endif
+
+#ifdef V8_OS_OPENBSD
+# define V8_TARGET_OS_OPENBSD
+# define V8_TARGET_OS_BSD
 #endif
 
 #ifdef V8_OS_MACOS
