diff --git a/index/gn/gnatprove/gnatprove-13.2.1.toml b/index/gn/gnatprove/gnatprove-13.2.1.toml
index eaa9e8842..233d6f2da 100644
--- a/index/gn/gnatprove/gnatprove-13.2.1.toml
+++ b/index/gn/gnatprove/gnatprove-13.2.1.toml
@@ -12,6 +12,7 @@ disabled = true
 
 [environment]
 PATH.prepend = "${CRATE_ROOT}/bin"
+GPR_PROJECT_PATH.prepend = "${CRATE_ROOT}/lib/gnat"
 
 [origin."case(os)".windows."case(host-arch)".x86-64]
 url = "https://github.com/alire-project/GNAT-FSF-builds/releases/download/gnatprove-13.2.0-1/gnatprove-x86_64-windows64-13.2.0-1.tar.gz"