diff -up ksh-20120801/src/cmd/ksh93/sh/macro.c.bz1222025 ksh-20120801/src/cmd/ksh93/sh/macro.c

--- ksh-20120801/src/cmd/ksh93/sh/macro.c.bz1222025	2015-09-15 17:28:47.304722569 +0200

+++ ksh-20120801/src/cmd/ksh93/sh/macro.c	2015-09-17 17:49:46.842891942 +0200

@@ -1195,6 +1195,13 @@ retry1:

 		}

 		else

 			v = 0;

+		if(!v && sh_isoption(SH_NOUNSET))

+		{

+			d=fcget();

+			fcseek(-1);

+			if(!(d && strchr(":+-?=",d)))

+				errormsg(SH_DICT,ERROR_exit(1),e_notset,ltos(c));

+		}

 		break;

 	    case S_ALP:

 		if(c=='.' && type==0)