diff --git a/pkgs/build-support/rust/build-rust-crate/configure-crate.nix b/pkgs/build-support/rust/build-rust-crate/configure-crate.nix
index 1c946764c758..5168eb6ab759 100644
--- a/pkgs/build-support/rust/build-rust-crate/configure-crate.nix
+++ b/pkgs/build-support/rust/build-rust-crate/configure-crate.nix
@@ -130,7 +130,7 @@ in ''
   export CARGO_CFG_UNIX=1
   export CARGO_CFG_TARGET_ENV="gnu"
   export CARGO_CFG_TARGET_ENDIAN=${if stdenv.hostPlatform.parsed.cpu.significantByte.name == "littleEndian" then "little" else "big"}
-  export CARGO_CFG_TARGET_POINTER_WIDTH=${toString stdenv.hostPlatform.parsed.cpu.bits}
+  export CARGO_CFG_TARGET_POINTER_WIDTH=${with stdenv.hostPlatform; toString (if isILP32 then 32 else parsed.cpu.bits)}
   export CARGO_CFG_TARGET_VENDOR=${stdenv.hostPlatform.parsed.vendor.name}
 
   export CARGO_MANIFEST_DIR=$(pwd)