--- src/cmd/ksh93/sh/lex.c
+++ src/cmd/ksh93/sh/lex.c	2012-01-16 16:09:37.624771155 +0100
@@ -1874,6 +1874,8 @@ static int here_copy(Lex_t *lp,register
 					sfputc(sp,'\\');
 				}
 			}
+			if (LEN < 1)
+				LEN = 1;
 			bufp = fcseek(-LEN);
 		}
 		else