diff --git a/pkgs/build-support/rust/default.nix b/pkgs/build-support/rust/default.nix
index cd19782e6115..c23581d96019 100644
--- a/pkgs/build-support/rust/default.nix
+++ b/pkgs/build-support/rust/default.nix
@@ -44,7 +44,7 @@ in stdenv.mkDerivation (args // {
     export CARGO_HOME="$(realpath deps)"
 
     # Let's find out which $indexHash cargo uses for file:///dev/null
-    (cd $sourceRoot && cargo fetch &>/dev/null)
+    (cd $sourceRoot && cargo fetch &>/dev/null) || true
     cd deps
     indexHash="$(basename $(echo registry/index/*))"