diff --git a/grep.c b/grep.c
index 2fbf5b6..28ff11a 100644
--- a/grep.c
+++ b/grep.c
@@ -14,8 +14,9 @@ grep(char *pattern, int fd)
   char *p, *q;
   
   m = 0;
-  while((n = read(fd, buf+m, sizeof(buf)-m)) > 0){
+  while((n = read(fd, buf+m, sizeof(buf)-m-1)) > 0){
     m += n;
+    buf[m] = '\0';
     p = buf;
     while((q = strchr(p, '\n')) != 0){
       *q = 0;