diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index bcadc42..ba95a67 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,7 +9,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-latest, windows-latest]
+        os: [ubuntu-latest, macos-latest, windows-latest]
     steps:
       - uses: actions/checkout@v2
       - uses: actions-rs/install@v0.1
diff --git a/CHANGELOG.md b/CHANGELOG.md
index dba3e81..d8c0be7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Nushell: errors on 0.33.0.
 - PowerShell: errors when initializing in `StrictMode`.
+- Bash/POSIX: remove conflicting alias definitions when initializing.
 
 ## [0.7.2] - 2021-06-10
 
diff --git a/shell.nix b/shell.nix
index 5111918..887f6a6 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,28 +1,36 @@
 let
-  pkgs = import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/20.09.tar.gz") {};
-  pkgs-master = import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/8e4c6b845965440850eaec79db7086e5d9e350fd.tar.gz") {};
-  pkgs-python = pkgs-master.python3.withPackages (pkgs: [ pkgs.black pkgs.mypy pkgs.pylint ]);
+  rust = import (builtins.fetchTarball "https://github.com/oxalica/rust-overlay/archive/master.tar.gz");
+  pkgs = import <nixpkgs> { overlays = [ rust ]; };
+  pkgs-latest = import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/94e725d3299cbeb71419758d671dfb0771b8e318.tar.gz") {};
+  pkgs-python = pkgs-latest.python3.withPackages (pkgs: [ pkgs.black pkgs.mypy pkgs.pylint ]);
 in
 pkgs.mkShell {
   buildInputs = [
-    pkgs-master.cargo-audit
-    pkgs-master.elvish
-    pkgs-master.nushell
-    pkgs-master.shellcheck
-    pkgs-master.shfmt
+    # Rust
+    pkgs.rust-bin.stable.latest.default
+
+    # Shells
+    pkgs-latest.bash
+    pkgs-latest.dash
+    pkgs-latest.elvish
+    pkgs-latest.nushell
+    pkgs-latest.fish
+    pkgs-latest.powershell
+    pkgs-latest.xonsh
+    pkgs-latest.zsh
+
+    # Linters
+    pkgs-latest.cargo-audit
+    pkgs-latest.shellcheck
+    pkgs-latest.shfmt
     pkgs-python
-    pkgs.bash
-    pkgs.cargo
-    pkgs.clippy
-    pkgs.dash
-    pkgs.fish
-    pkgs.fzf
-    pkgs.git
-    pkgs.powershell
-    pkgs.rustc
-    pkgs.rustfmt
-    pkgs.xonsh
-    pkgs.zsh
+
+    # Dependencies
+    pkgs.cacert
+    pkgs.libiconv
+    pkgs-latest.fzf
+    pkgs-latest.git
   ];
+
   RUST_BACKTRACE = 1;
 }
diff --git a/src/shell.rs b/src/shell.rs
index dc7efa7..48d60f5 100644
--- a/src/shell.rs
+++ b/src/shell.rs
@@ -399,7 +399,7 @@ mod tests {
         let source = Zsh(&opts).render().unwrap();
 
         Command::new("zsh")
-            .args(&["-c", &source, "--no-rcs"])
+            .args(&["-c", &source, "--no-globalrcs", "--no-rcs"])
             .assert()
             .success()
             .stdout("")
diff --git a/templates/bash.txt b/templates/bash.txt
index e0b1cef..9a11b5f 100644
--- a/templates/bash.txt
+++ b/templates/bash.txt
@@ -109,10 +109,9 @@ function __zoxide_zi() {
 
 # Remove definitions.
 function __zoxide_unset() {
-    # shellcheck disable=SC1001
     \builtin unset -f "$@" &>/dev/null
-    # shellcheck disable=SC1001
     \builtin unset -v "$@" &>/dev/null
+    \builtin unalias "$@" &>/dev/null || \builtin :
 }
 
 __zoxide_unset '{{cmd}}'
diff --git a/templates/posix.txt b/templates/posix.txt
index 05a776a..add0121 100644
--- a/templates/posix.txt
+++ b/templates/posix.txt
@@ -92,10 +92,10 @@ __zoxide_zi() {
 
 # Remove definitions.
 __zoxide_unset() {
-    # shellcheck disable=SC1001
     \unset -f "$@" >/dev/null 2>&1
-    # shellcheck disable=SC1001
     \unset -v "$@" >/dev/null 2>&1
+    # shellcheck disable=SC1001
+    \unalias "$@" >/dev/null 2>&1 || \:
 }
 
 __zoxide_unset '{{cmd}}'