diff --git a/sys/src/cmd/sam/shell.c b/sys/src/cmd/sam/shell.c
index 7c3a0b25c..494bbf4a3 100644
--- a/sys/src/cmd/sam/shell.c
+++ b/sys/src/cmd/sam/shell.c
@@ -93,7 +93,7 @@ plan9(File *f, int type, String *s, int nest)
 			close(0);	/* so it won't read from terminal */
 			open("/dev/null", 0);
 		}
-		putenv("f", Strtoc(&f->name));
+		putenv("%", Strtoc(&f->name));
 		execl(SHPATH, SH, "-c", Strtoc(&plan9cmd), nil);
 		exits("exec");
 	}