diff --git a/pkgs/build-support/node/fetch-yarn-deps/default.nix b/pkgs/build-support/node/fetch-yarn-deps/default.nix
index 19b7eeaee7a5..e0c790e1c874 100644
--- a/pkgs/build-support/node/fetch-yarn-deps/default.nix
+++ b/pkgs/build-support/node/fetch-yarn-deps/default.nix
@@ -136,6 +136,8 @@ in
               cacert
             ];
 
+            impureEnvVars = lib.fetchers.proxyImpureEnvVars;
+
             env = {
               GIT_SSL_CAINFO = "${cacert}/etc/ssl/certs/ca-bundle.crt";
               NODE_EXTRA_CA_CERTS = "${cacert}/etc/ssl/certs/ca-bundle.crt";