diff --git a/runtime/doc/change.txt b/runtime/doc/change.txt
index e82256d..c1eed2c 100644
--- a/runtime/doc/change.txt
+++ b/runtime/doc/change.txt
@@ -1571,6 +1571,10 @@
 			in their original order, right before the sorted
 			lines.
 
+			If {pattern} is empty (e.g. // is specified), the
+			last search pattern is used.  This allows trying out
+			a pattern first.
+
 Note that using ":sort" with ":global" doesn't sort the matching lines, it's
 quite useless.
 
diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index 5ca3dfd..66bbb18 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -408,7 +408,11 @@
 		goto sortend;
 	    }
 	    *s = NUL;
-	    regmatch.regprog = vim_regcomp(p + 1, RE_MAGIC);
+	    /* Use last search pattern if sort pattern is empty. */
+	    if (s == p + 1 && last_search_pat() != NULL)
+		regmatch.regprog = vim_regcomp(last_search_pat(), RE_MAGIC);
+	    else
+		regmatch.regprog = vim_regcomp(p + 1, RE_MAGIC);
 	    if (regmatch.regprog == NULL)
 		goto sortend;
 	    p = s;		/* continue after the regexp */
diff --git a/src/version.c b/src/version.c
index 38095cb..23a7348 100644
--- a/src/version.c
+++ b/src/version.c
@@ -667,6 +667,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    28,
+/**/
     27,
 /**/
     26,