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)