diff --git a/nixos/modules/config/shells-environment.nix b/nixos/modules/config/shells-environment.nix
index 555db459f57..6379b52870e 100644
--- a/nixos/modules/config/shells-environment.nix
+++ b/nixos/modules/config/shells-environment.nix
@@ -108,14 +108,14 @@ in
     };
 
     environment.shellAliases = mkOption {
-      default = {};
-      example = { ll = "ls -l"; };
+      example = { l = null; ll = "ls -l"; };
       description = ''
         An attribute set that maps aliases (the top level attribute names in
         this option) to command strings or directly to build outputs. The
         aliases are added to all users' shells.
+        Aliases mapped to <code>null</code> are ignored.
       '';
-      type = types.attrs; # types.attrsOf types.stringOrPath;
+      type = with types; attrsOf (nullOr (either str path));
     };
 
     environment.binsh = mkOption {
@@ -157,6 +157,12 @@ in
     # terminal instead of logging out of X11).
     environment.variables = config.environment.sessionVariables;
 
+    environment.shellAliases = mapAttrs (name: mkDefault) {
+      ls = "ls --color=tty";
+      ll = "ls -l";
+      l  = "ls -alh";
+    };
+
     environment.etc."shells".text =
       ''
         ${concatStringsSep "\n" (map utils.toShellPath cfg.shells)}
diff --git a/nixos/modules/programs/bash/bash.nix b/nixos/modules/programs/bash/bash.nix
index f664e222555..0fbc77ea44c 100644
--- a/nixos/modules/programs/bash/bash.nix
+++ b/nixos/modules/programs/bash/bash.nix
@@ -33,7 +33,8 @@ let
   '';
 
   bashAliases = concatStringsSep "\n" (
-    mapAttrsFlatten (k: v: "alias ${k}=${escapeShellArg v}") cfg.shellAliases
+    mapAttrsFlatten (k: v: "alias ${k}=${escapeShellArg v}")
+      (filterAttrs (k: v: !isNull v) cfg.shellAliases)
   );
 
 in
@@ -59,12 +60,12 @@ in
       */
 
       shellAliases = mkOption {
-        default = config.environment.shellAliases;
+        default = {};
         description = ''
-          Set of aliases for bash shell. See <option>environment.shellAliases</option>
-          for an option format description.
+          Set of aliases for bash shell, which overrides <option>environment.shellAliases</option>.
+          See <option>environment.shellAliases</option> for an option format description.
         '';
-        type = types.attrs; # types.attrsOf types.stringOrPath;
+        type = with types; attrsOf (nullOr (either str path));
       };
 
       shellInit = mkOption {
@@ -125,6 +126,8 @@ in
 
     programs.bash = {
 
+      shellAliases = mapAttrs (name: mkDefault) cfge.shellAliases;
+
       shellInit = ''
         if [ -z "$__NIXOS_SET_ENVIRONMENT_DONE" ]; then
             . ${config.system.build.setEnvironment}
diff --git a/nixos/modules/programs/fish.nix b/nixos/modules/programs/fish.nix
index 5948fe11f92..b38af07b92c 100644
--- a/nixos/modules/programs/fish.nix
+++ b/nixos/modules/programs/fish.nix
@@ -9,7 +9,8 @@ let
   cfg = config.programs.fish;
 
   fishAliases = concatStringsSep "\n" (
-    mapAttrsFlatten (k: v: "alias ${k} ${escapeShellArg v}") cfg.shellAliases
+    mapAttrsFlatten (k: v: "alias ${k} ${escapeShellArg v}")
+      (filterAttrs (k: v: !isNull v) cfg.shellAliases)
   );
 
 in
@@ -53,12 +54,12 @@ in
       };
 
       shellAliases = mkOption {
-        default = config.environment.shellAliases;
+        default = {};
         description = ''
-          Set of aliases for fish shell. See <option>environment.shellAliases</option>
-          for an option format description.
+          Set of aliases for fish shell, which overrides <option>environment.shellAliases</option>.
+          See <option>environment.shellAliases</option> for an option format description.
         '';
-        type = types.attrs;
+        type = with types; attrsOf (nullOr (either str path));
       };
 
       shellInit = mkOption {
@@ -99,6 +100,8 @@ in
 
   config = mkIf cfg.enable {
 
+    programs.fish.shellAliases = mapAttrs (name: mkDefault) cfge.shellAliases;
+
     environment.etc."fish/foreign-env/shellInit".text = cfge.shellInit;
     environment.etc."fish/foreign-env/loginShellInit".text = cfge.loginShellInit;
     environment.etc."fish/foreign-env/interactiveShellInit".text = cfge.interactiveShellInit;
diff --git a/nixos/modules/programs/shell.nix b/nixos/modules/programs/shell.nix
index 944a8bdf16f..6aa0262e3a4 100644
--- a/nixos/modules/programs/shell.nix
+++ b/nixos/modules/programs/shell.nix
@@ -8,12 +8,6 @@ with lib;
 
   config = {
 
-    environment.shellAliases =
-      { ls = "ls --color=tty";
-        ll = "ls -l";
-        l  = "ls -alh";
-      };
-
     environment.shellInit =
       ''
         # Set up the per-user profile.
diff --git a/nixos/modules/programs/zsh/zsh.nix b/nixos/modules/programs/zsh/zsh.nix
index 865d148c162..164d8db5859 100644
--- a/nixos/modules/programs/zsh/zsh.nix
+++ b/nixos/modules/programs/zsh/zsh.nix
@@ -11,7 +11,8 @@ let
   cfg = config.programs.zsh;
 
   zshAliases = concatStringsSep "\n" (
-    mapAttrsFlatten (k: v: "alias ${k}=${escapeShellArg v}") cfg.shellAliases
+    mapAttrsFlatten (k: v: "alias ${k}=${escapeShellArg v}")
+      (filterAttrs (k: v: !isNull v) cfg.shellAliases)
   );
 
 in
@@ -34,13 +35,12 @@ in
       };
 
       shellAliases = mkOption {
-        default = config.environment.shellAliases;
+        default = {};
         description = ''
-          Set of aliases for zsh shell. Overrides the default value taken from
-           <option>environment.shellAliases</option>.
+          Set of aliases for zsh shell, which overrides <option>environment.shellAliases</option>.
           See <option>environment.shellAliases</option> for an option format description.
         '';
-        type = types.attrs; # types.attrsOf types.stringOrPath;
+        type = with types; attrsOf (nullOr (either str path));
       };
 
       shellInit = mkOption {
@@ -106,6 +106,8 @@ in
 
   config = mkIf cfg.enable {
 
+    programs.zsh.shellAliases = mapAttrs (name: mkDefault) cfge.shellAliases;
+
     environment.etc."zshenv".text =
       ''
         # /etc/zshenv: DO NOT EDIT -- this file has been generated automatically.