diff --git a/index/gn/gnatcov/gnatcov-21.0.1.toml b/index/gn/gnatcov/gnatcov-21.0.1.toml
index 0a878706..20d4f840 100644
--- a/index/gn/gnatcov/gnatcov-21.0.1.toml
+++ b/index/gn/gnatcov/gnatcov-21.0.1.toml
@@ -9,6 +9,7 @@ auto-gpr-with = false
 
 [environment]
 PATH.prepend = "${CRATE_ROOT}/bin"
+GPR_PROJECT_PATH.append= "${CRATE_ROOT}/share/gnatcoverage/gnatcov_rts/"
 
 [origin."case(os)".linux."case(word-size)".bits-64]
 url = "https://github.com/alire-project/GNAT-FSF-builds/releases/download/gnatcov-21.0-1/gnatcov-x86_64-linux-21.0-1.tar.gz"
diff --git a/index/gn/gnatcov/gnatcov-21.0.2.toml b/index/gn/gnatcov/gnatcov-21.0.2.toml
index 06a7f213..2506dec7 100644
--- a/index/gn/gnatcov/gnatcov-21.0.2.toml
+++ b/index/gn/gnatcov/gnatcov-21.0.2.toml
@@ -9,6 +9,7 @@ auto-gpr-with = false
 
 [environment]
 PATH.prepend = "${CRATE_ROOT}/bin"
+GPR_PROJECT_PATH.append= "${CRATE_ROOT}/share/gnatcoverage/gnatcov_rts/"
 
 [origin."case(os)".linux."case(word-size)".bits-64]
 url = "https://github.com/alire-project/GNAT-FSF-builds/releases/download/gnatcov-21.0-2/gnatcov-x86_64-linux-21.0-2.tar.gz"