diff --git a/sys/src/cmd/cc/lex.c b/sys/src/cmd/cc/lex.c
index 2652cb8f8..74054aa22 100644
--- a/sys/src/cmd/cc/lex.c
+++ b/sys/src/cmd/cc/lex.c
@@ -1262,7 +1262,9 @@ loop:
 	if(i->f < 0)
 		goto pop;
 	fi.c = read(i->f, i->b, BUFSIZ) - 1;
-	if(fi.c < 0) {
+	if(fi.c < -1)
+		sysfatal("read error: %r");
+	if(fi.c == -1) {
 		close(i->f);
 		linehist(0, 0);
 		goto pop;