MacRuby requires <file>.rbo instead of <file>.rb when you write 'require "<file>.rb"' in your script and <file>.rbo was created recently

load.c.patch

diff --git a/load.c b/load.c
index b070a12..bc00930 100644
--- a/load.c
+++ b/load.c
@@ -323,6 +323,15 @@ check_path(const char *path, VALUE *out, int *type)
 	// it's a valid one, then try to validate the path.
 	int t = 0;
 	if (strcmp(p + 1, "rb") == 0) {
+	    if (rbo_enabled && strlen(path) < (PATH_MAX - 1)) {
+		char buf[PATH_MAX];
+		strcpy(buf, path);
+		strcat(buf, "o");
+		if (path_ok(buf, out)) {
+		    *type = TYPE_RBO;
+		    return true;
+		}
+	    }
 	    t = TYPE_RB;
 	}
 	else if (rbo_enabled && strcmp(p + 1, "rbo") == 0) {