diff --git a/index/gn/gnatcoll/gnatcoll-22.0.0.toml b/index/gn/gnatcoll/gnatcoll-22.0.0.toml
index 9e1067e3..40a0a241 100644
--- a/index/gn/gnatcoll/gnatcoll-22.0.0.toml
+++ b/index/gn/gnatcoll/gnatcoll-22.0.0.toml
@@ -27,6 +27,7 @@ GNATCOLL_OS = "windows"
 
 [gpr-set-externals]
 GNATCOLL_VERSION = "22.0.0"
+GNATCOLL_BUILD_MODE = "PROD"
 
 [[depends-on]]
 libgpr = "~22.0.0"