diff --git a/src/docs/part1/simple_detector.md b/src/docs/part1/simple_detector.md
index dc6fa1995e85e809b2d6f09b536837c0e05f62c4..60ce9a63fdf75db3f6e0b7eb8ddaeab2863abdc7 100644
--- a/src/docs/part1/simple_detector.md
+++ b/src/docs/part1/simple_detector.md
@@ -64,7 +64,7 @@ Examine the compact description, specifically this part:
 checkOverlaps -t 0.0001 -c gem_tracker.xml
 ```
 
-```
+```bash
 ...
 Info in <TGeoNodeMatrix::CheckOverlaps>: Checking overlaps for world_volume and daughters within 0.0001
 Check overlaps:      [==========]   11 [100.00 %]           00:00