diff --git a/pkgs/build-support/rust/build-rust-crate/build-crate.nix b/pkgs/build-support/rust/build-rust-crate/build-crate.nix
index e842b6a3f501..bbb26606a6a4 100644
--- a/pkgs/build-support/rust/build-rust-crate/build-crate.nix
+++ b/pkgs/build-support/rust/build-rust-crate/build-crate.nix
@@ -51,7 +51,7 @@
     # configure & source common build functions
     LIB_RUSTC_OPTS="${libRustcOpts}"
     BIN_RUSTC_OPTS="${binRustcOpts}"
-    LIB_EXT="${stdenv.hostPlatform.extensions.sharedLibrary}"
+    LIB_EXT="${stdenv.hostPlatform.extensions.sharedLibrary or ""}"
     LIB_PATH="${libPath}"
     LIB_NAME="${libName}"