diff --git a/.evergreen/auth_oidc/gcp/setup.sh b/.evergreen/auth_oidc/gcp/setup.sh
index eb9e7a0c..83c3837f 100755
--- a/.evergreen/auth_oidc/gcp/setup.sh
+++ b/.evergreen/auth_oidc/gcp/setup.sh
@@ -98,7 +98,7 @@ URI=$(check_deployment)
 
 cat <<EOF >> "secrets-export.sh"
 export MONGODB_URI="$URI"
-export MONGODB_URI_SINGLE="$URI/?authMechanism=MONGODB-OIDC&authMechanismProperties=ENVIRONMENT:gcp,TOKEN_RESOURCE:$GCPOIDC_AUDIENCE"
+export MONGODB_URI_SINGLE="$URI/?authMechanism=MONGODB-OIDC&authSource=%24external&authMechanismProperties=ENVIRONMENT:gcp,TOKEN_RESOURCE:$GCPOIDC_AUDIENCE"
 export OIDC_ADMIN_USER=$GCPOIDC_ATLAS_USER
 export OIDC_ADMIN_PWD=$GCPOIDC_ATLAS_PASSWORD
 EOF
diff --git a/.evergreen/auth_oidc/setup.sh b/.evergreen/auth_oidc/setup.sh
index 797563f5..a8ce00d6 100755
--- a/.evergreen/auth_oidc/setup.sh
+++ b/.evergreen/auth_oidc/setup.sh
@@ -97,7 +97,7 @@ EOF
   URI=$(check_deployment)
   cat <<EOF >> "secrets-export.sh"
 export MONGODB_URI="$URI"
-export MONGODB_URI_SINGLE="$URI/?authMechanism=MONGODB-OIDC"
+export MONGODB_URI_SINGLE="$URI/?authMechanism=MONGODB-OIDC&authSource=%24external"
 export OIDC_ADMIN_USER=$OIDC_ATLAS_USER
 export OIDC_ADMIN_PWD=$OIDC_ATLAS_PASSWORD
 EOF