diff --git a/src/main.rs b/src/main.rs
index f6edf2b5..2af2eb71 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -143,10 +143,10 @@ fn run() -> Result<()> {
     #[cfg(unix)]
     {
         runner.execute(Step::Brew, "Brew", || unix::run_brew(&ctx))?;
-        runner.execute(Step::Brew, "Brew Cask", || unix::run_brew_cask(&ctx))?;
 
         #[cfg(target_os = "macos")]
         {
+            runner.execute(Step::Brew, "Brew Cask", || macos::run_brew_cask(&ctx))?;
             runner.execute(Step::MacPorts, "MacPorts", || macos::run_macports(&ctx))?;
             runner.execute(Step::MicrosoftAutoUpdate, "Microsoft AutoUpdate", || {
                 macos::run_msupdate(&ctx)
diff --git a/src/steps/os/macos.rs b/src/steps/os/macos.rs
index dc240c9f..609b6c44 100644
--- a/src/steps/os/macos.rs
+++ b/src/steps/os/macos.rs
@@ -1,5 +1,5 @@
 use crate::execution_context::ExecutionContext;
-use crate::executor::RunType;
+use crate::executor::{CommandExt, RunType};
 use crate::terminal::{print_separator, prompt_yesno};
 use crate::{
     error::{SkipStep, TopgradeError},
@@ -19,6 +19,40 @@ pub fn run_msupdate(ctx: &ExecutionContext) -> Result<()> {
     ctx.run_type().execute(msupdate).arg("--install").check_run()
 }
 
+pub fn run_brew_cask(ctx: &ExecutionContext) -> Result<()> {
+    let brew = require("brew")?;
+    print_separator("Brew Cask");
+
+    let config = ctx.config();
+    let run_type = ctx.run_type();
+
+    let cask_upgrade_exists = Command::new(&brew)
+        .args(&["--repository", "buo/cask-upgrade"])
+        .check_output()
+        .map(|p| Path::new(p.trim()).exists())?;
+
+    let cask_args = if cask_upgrade_exists {
+        let mut args = vec!["cu", "-y"];
+        if config.brew_cask_greedy() {
+            args.push("-a");
+        }
+        args
+    } else {
+        let mut args = vec!["cask", "upgrade"];
+        if config.brew_cask_greedy() {
+            args.push("--greedy");
+        }
+        args
+    };
+    run_type.execute(&brew).args(&cask_args).check_run()?;
+
+    if ctx.config().cleanup() {
+        run_type.execute(&brew).arg("cleanup").check_run()?;
+    }
+
+    Ok(())
+}
+
 pub fn run_macports(ctx: &ExecutionContext) -> Result<()> {
     require("port")?;
     let sudo = ctx.sudo().as_ref().unwrap();
diff --git a/src/steps/os/unix.rs b/src/steps/os/unix.rs
index 3744baee..8d4ec554 100644
--- a/src/steps/os/unix.rs
+++ b/src/steps/os/unix.rs
@@ -2,7 +2,7 @@
 use crate::error::SkipStep;
 use crate::error::TopgradeError;
 use crate::execution_context::ExecutionContext;
-use crate::executor::{CommandExt, ExecutorExitStatus, RunType};
+use crate::executor::{ExecutorExitStatus, RunType};
 use crate::terminal::{print_separator, print_warning};
 use crate::utils::{require, PathExt};
 use anyhow::Result;
@@ -11,7 +11,7 @@ use log::debug;
 use std::env;
 use std::fs;
 use std::os::unix::fs::MetadataExt;
-use std::path::{Path, PathBuf};
+use std::path::PathBuf;
 use std::process::Command;
 
 pub fn run_fisher(base_dirs: &BaseDirs, run_type: RunType) -> Result<()> {
@@ -42,40 +42,6 @@ pub fn run_brew(ctx: &ExecutionContext) -> Result<()> {
         .check_run()
 }
 
-pub fn run_brew_cask(ctx: &ExecutionContext) -> Result<()> {
-    let brew = require("brew")?;
-    print_separator("Brew Cask");
-
-    let config = ctx.config();
-    let run_type = ctx.run_type();
-
-    let cask_upgrade_exists = Command::new(&brew)
-        .args(&["--repository", "buo/cask-upgrade"])
-        .check_output()
-        .map(|p| Path::new(p.trim()).exists())?;
-
-    let cask_args = if cask_upgrade_exists {
-        let mut args = vec!["cu", "-y"];
-        if config.brew_cask_greedy() {
-            args.push("-a");
-        }
-        args
-    } else {
-        let mut args = vec!["cask", "upgrade"];
-        if config.brew_cask_greedy() {
-            args.push("--greedy");
-        }
-        args
-    };
-    run_type.execute(&brew).args(&cask_args).check_run()?;
-
-    if ctx.config().cleanup() {
-        run_type.execute(&brew).arg("cleanup").check_run()?;
-    }
-
-    Ok(())
-}
-
 pub fn run_nix(ctx: &ExecutionContext) -> Result<()> {
     let nix = require("nix")?;
     let nix_channel = require("nix-channel")?;