diff --git a/pkgs/by-name/ko/koboldcpp/package.nix b/pkgs/by-name/ko/koboldcpp/package.nix
index c096948565b0..bc64a8d9e0fe 100644
--- a/pkgs/by-name/ko/koboldcpp/package.nix
+++ b/pkgs/by-name/ko/koboldcpp/package.nix
@@ -129,7 +129,7 @@ effectiveStdenv.mkDerivation (finalAttrs: {
     (makeBool "LLAMA_CLBLAST" clblastSupport)
     (makeBool "LLAMA_VULKAN" vulkanSupport)
     (makeBool "LLAMA_METAL" metalSupport)
-    (lib.optionalString cublasSupport "CUDA_DOCKER_ARCH=sm_${builtins.head cudaArches}")
+    (lib.optionals cublasSupport "CUDA_DOCKER_ARCH=sm_${builtins.head cudaArches}")
   ];
 
   installPhase = ''