diff --git a/docs/usage.md b/docs/usage.md
index d4eb5db..9539a5a 100644
--- a/docs/usage.md
+++ b/docs/usage.md
@@ -471,10 +471,10 @@ Centrifuge allows the user to [build custom databases](https://ccb.jhu.edu/softw
 
 An example of custom `seqid2taxid.map`:
 
-NC_001133.9    4392
-NC_012920.1    9606
-NC_001134.8    4392
-NC_001135.5    4392
+NC_001133.9 4392
+NC_012920.1 9606
+NC_001134.8 4392
+NC_001135.5 4392
 
 ```bash
 centrifuge-download -o taxonomy taxonomy