diff --git a/B-mass-model.md b/B-mass-model.md
index e969bd0..bc5c3b7 100644
--- a/B-mass-model.md
+++ b/B-mass-model.md
@@ -57,6 +57,15 @@ This will fail if you already sourced ROOT or python [described here](https://gi
 cd Code/Selection/RooFit/RooExpAndGauss/
 make 
 ```
+### Recompile Mass Fit 
+
+Now we need to link the RooFit models to MassFit.cpp by recompiling it in ROOT
+
+```
+root
+ .L MassFit.cpp+
+ .q
+```
 
 ## Fit model description
 The fit is defined in the `massFit` function in  [[MassFit.cpp|MassFit.cpp]]. The user can decide