diff --git a/modules/programs/zsh.nix b/modules/programs/zsh.nix
index 34df1a76..d69ea7c3 100644
--- a/modules/programs/zsh.nix
+++ b/modules/programs/zsh.nix
@@ -613,7 +613,7 @@ in
           source ${cfg.syntaxHighlighting.package}/share/zsh-syntax-highlighting/zsh-syntax-highlighting.zsh
           ${lib.concatStringsSep "\n" (
               lib.mapAttrsToList
-                (name: value: "ZSH_HIGHLIGHT_STYLES[${lib.escapeShellArg name}]=${lib.escapeShellArg value}")
+                (name: value: "ZSH_HIGHLIGHT_STYLES+=(${lib.escapeShellArg name} ${lib.escapeShellArg value})")
                 cfg.syntaxHighlighting.styles
           )}
         '')
diff --git a/tests/modules/programs/zsh/syntax-highlighting.nix b/tests/modules/programs/zsh/syntax-highlighting.nix
index be2ad37e..73297c8c 100644
--- a/tests/modules/programs/zsh/syntax-highlighting.nix
+++ b/tests/modules/programs/zsh/syntax-highlighting.nix
@@ -17,7 +17,7 @@ with lib;
 
     nmt.script = ''
       assertFileContains home-files/.zshrc "source ${pkgs.hello}/share/zsh-syntax-highlighting/zsh-syntax-highlighting.zsh"
-      assertFileContains home-files/.zshrc "ZSH_HIGHLIGHT_STYLES['comment']='fg=#6c6c6c'"
+      assertFileContains home-files/.zshrc "ZSH_HIGHLIGHT_STYLES+=('comment' 'fg=#6c6c6c')"
     '';
   };
 }