diff --git a/README.md b/README.md
index c30d00d..6923aa1 100644
--- a/README.md
+++ b/README.md
@@ -58,6 +58,12 @@ link `ca65Label` (or `ca65Opcode`) to another class, eg:
 hi link ca65Label Typedef
 ```
 
+You can add syntax highlighting for your own assembler like this:
+```vim
+" in ~/.vim/ftplugin/ca65.vim
+syn keyword ca65customMacros Macro1 Macro2 mul div macro3
+```
+
 ### Header/Source split function
 To use the source-header split function, map it and set your preferred assembly filetypes:
 ```vim
diff --git a/syntax/ca65.vim b/syntax/ca65.vim
index 861bf65..60643d9 100644
--- a/syntax/ca65.vim
+++ b/syntax/ca65.vim
@@ -23,9 +23,6 @@ syn clear
 syn case ignore
 syntax iskeyword @,48-57,192-255,$,_,.,*
 
-" custom macros
-syn keyword customMacros Import Export Print Strf div
-
 " registers
 syn keyword ca65Reg x y a
 
@@ -116,7 +113,7 @@ hi link ca65PseudoFunctions   PreProc
 hi link ca65ControlCommands   PreProc
 hi link ca65MacLongbranch	  PreProc
 hi link ca65MacGeneric	      PreProc
-hi link customMacros	      PreProc
+hi link ca65customMacros	  PreProc
 " INSTRUCTIONS
 hi link ca6502Opcode          ca65Opcode
 hi link ca65C02Opcode         ca65Opcode