diff --git a/bash-abbr b/bash-abbr
index d0bbb37..8d27df8 100644
--- a/bash-abbr
+++ b/bash-abbr
@@ -153,7 +153,8 @@ _redir_or_assign_word () {
                _simple_variable='\$([[:alpha:]_][[:alnum:]]*|[-_$!*#[:digit:]])' \
                _advanced_variable='\$\{([[:alpha:]_][[:alnum:]]*|[-_$!*#[:digit:]])[^}]*\}' \
                _deprecated_arithmetic_eval='\$\[[^][]*\]' \
-               _cmd_subst_or_arithmetic_eval='\$\([^()]*\)' \
+               _cmd_subst='\$\([^()]*\)' \
+               _arithmetic_eval='\$\(\([^()]*\)\)' \
                _process_substition='<\([^()]*\)' \
                _escaped_char='\\.'
     declare _part="$_simple_unquoted_word"
@@ -163,7 +164,8 @@ _redir_or_assign_word () {
     _part+="|$_simple_variable"
     _part+="|$_advanced_variable"
     _part+="|$_deprecated_arithmetic_eval"
-    _part+="|$_cmd_subst_or_arithmetic_eval"
+    _part+="|$_cmd_subst"
+    _part+="|$_arithmetic_eval"
     _part+="|$_process_substition"
     _part+="|$_escaped_char"
     declare -r _word="($_part)+" \