diff --git a/joss/paper.md b/joss/paper.md
index efee481..bc8d953 100644
--- a/joss/paper.md
+++ b/joss/paper.md
@@ -9,16 +9,16 @@ authors:
   - name: Beatriz Costa-Gomes
     equal-contrib: true
     corresponding: true
-    affiliation: 1
+    affiliation: '1'
   - name: Oliver Strickson
     equal-contrib: true 
-    affiliation: 1
+    affiliation: '1'
   - name: Joel Greer
     equal-contrib: true
-    affiliation: 2
+    affiliation: '2'
   - name: Alan R. Lowe
     corresponding: true
-    affiliation: 1,3
+    affiliation: '1, 3'
      
 affiliations:
  - name: The Alan Turing Institute, London, England, NW1 2DB, United Kingdom