diff --git a/src/option.h b/src/option.h
index cb25938..50fe380 100644
--- a/src/option.h
+++ b/src/option.h
@@ -101,10 +101,11 @@
 #define FO_WHITE_PAR	'w'	/* trailing white space continues paragr. */
 #define FO_AUTO		'a'	/* automatic formatting */
 #define FO_REMOVE_COMS	'j'	/* remove comment leaders when joining lines */
+#define FO_PERIOD_ABBR	'p'	/* don't break a single space after a period */
 
 #define DFLT_FO_VI	"vt"
 #define DFLT_FO_VIM	"tcq"
-#define FO_ALL		"tcroq2vlb1mMBn,awj"	/* for do_set() */
+#define FO_ALL		"tcroq2vlb1mMBn,awjp"	/* for do_set() */
 
 /* characters for the p_cpo option: */
 #define CPO_ALTREAD	'a'	/* ":read" sets alternate file name */