diff --git a/default.nix b/default.nix
index 61b44ec..a377938 100644
--- a/default.nix
+++ b/default.nix
@@ -31,7 +31,7 @@ let
         libb.findGitDependencies { inherit (config) cargolock gitAllRefs gitSubmodules; };
       cargoconfig =
         if builtinz.pathExists (toString config.root + "/.cargo/config")
-        then builtins.readFile (config.root + "/.cargo/config")
+        then (config.root + "/.cargo/config")
         else null;
       build = args: import ./build.nix (
         {
diff --git a/test/fast/cargo-config/default.nix b/test/fast/cargo-config/default.nix
new file mode 100644
index 0000000..d34c380
--- /dev/null
+++ b/test/fast/cargo-config/default.nix
@@ -0,0 +1,6 @@
+{ naersk, ... }:
+
+naersk.buildPackage {
+  src = ./fixtures;
+  doCheck = true;
+}
diff --git a/test/fast/cargo-config/fixtures/.cargo/config b/test/fast/cargo-config/fixtures/.cargo/config
new file mode 100644
index 0000000..ac0cce0
--- /dev/null
+++ b/test/fast/cargo-config/fixtures/.cargo/config
@@ -0,0 +1,2 @@
+[env]
+ENV_HELLO_WORLD="Hello, World!"
diff --git a/test/fast/cargo-config/fixtures/Cargo.lock b/test/fast/cargo-config/fixtures/Cargo.lock
new file mode 100644
index 0000000..c469709
--- /dev/null
+++ b/test/fast/cargo-config/fixtures/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "cargo-config"
+version = "0.1.0"
diff --git a/test/fast/cargo-config/fixtures/Cargo.toml b/test/fast/cargo-config/fixtures/Cargo.toml
new file mode 100644
index 0000000..da3a97d
--- /dev/null
+++ b/test/fast/cargo-config/fixtures/Cargo.toml
@@ -0,0 +1,4 @@
+[package]
+name = "cargo-config"
+version = "0.1.0"
+edition = "2021"
diff --git a/test/fast/cargo-config/fixtures/src/main.rs b/test/fast/cargo-config/fixtures/src/main.rs
new file mode 100644
index 0000000..c11d46f
--- /dev/null
+++ b/test/fast/cargo-config/fixtures/src/main.rs
@@ -0,0 +1,11 @@
+fn main() {
+    println!("{}", env!("ENV_HELLO_WORLD"));
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test() {
+        assert_eq!("Hello, World!", env!("ENV_HELLO_WORLD"));
+    }
+}
diff --git a/test/fast/default.nix b/test/fast/default.nix
index 18582e4..ee063b2 100644
--- a/test/fast/default.nix
+++ b/test/fast/default.nix
@@ -1,4 +1,5 @@
 args: {
+  cargo-config = import ./cargo-config args;
   cargo-wildcard = import ./cargo-wildcard args;
   default-run = import ./default-run args;
   dummyfication = import ./dummyfication args;