diff --git a/get_next_line.h b/get_next_line.h
index 88f517f..fa73905 100644
--- a/get_next_line.h
+++ b/get_next_line.h
@@ -19,6 +19,9 @@
 # ifndef BUFFER_SIZE
 #  define BUFFER_SIZE 1024
 # endif
+# if BUFFER_SIZE <= 1
+#  error BUFFER_SIZE must be at least 2
+# endif
 
 char	*get_next_line(int fd);