diff --git a/readme.md b/readme.md
index 23d7c79..b36a70f 100644
--- a/readme.md
+++ b/readme.md
@@ -8,7 +8,7 @@
    1. [RUNNING THE PROGRAM](#running-the-program)
    2. [COMMAND LINE OPTIONS](#command-line-options)
    3. [INTERACTIVE INTERFACE](#interactive-interface)
-   4. [INPUT/OUTPUT](#inputoutput)
+   4. [INPUT/OUTPUT](#input-output)
       1. Cell Sample Files
       2. Sample Plate Files
       3. Graph/Data Files