diff --git a/modoboa_installer/compatibility_matrix.py b/modoboa_installer/compatibility_matrix.py
index dbb92d8..e399143 100644
--- a/modoboa_installer/compatibility_matrix.py
+++ b/modoboa_installer/compatibility_matrix.py
@@ -2,8 +2,9 @@
 
 COMPATIBILITY_MATRIX = {
     "1.8.1": {
-        "modoboa-webmail": "<=1.1.5",
+        "modoboa-pdfcredentials": "<=1.1.0",
         "modoboa-sievefilers": "<=1.1.0",
+        "modoboa-webmail": "<=1.1.5",
     }
 }