diff --git a/pkgs/development/compilers/swift/compiler/default.nix b/pkgs/development/compilers/swift/compiler/default.nix
index c23b8e0877f5..993ca970c06e 100644
--- a/pkgs/development/compilers/swift/compiler/default.nix
+++ b/pkgs/development/compilers/swift/compiler/default.nix
@@ -484,6 +484,7 @@ stdenv.mkDerivation {
             "aarch64" = "AArch64";
           }
           .${targetPlatform.parsed.cpu.name}
+            or (throw "Unsupported CPU architecture: ${targetPlatform.parsed.cpu.name}")
         }
       "
       buildProject llvm llvm-project/llvm