diff --git a/lips/Lexer.lua b/lips/Lexer.lua
index c5843c2..2e5d1af 100644
--- a/lips/Lexer.lua
+++ b/lips/Lexer.lua
@@ -335,8 +335,11 @@ function Lexer:lex(_yield)
             self:nextc()
             local buff = self:read_chars('[%w]')
             local up = buff:upper()
+            if data.directive_aliases[up] then
+                up = data.directive_aliases[up]
+            end
             if not data.all_directives[up] then
-                self:error('not a directive')
+                self:error('unknown directive')
             end
             if up == 'INC' or up == 'INCASM' or up == 'INCLUDE' then
                 yield('DIR', 'INC')
diff --git a/lips/data.lua b/lips/data.lua
index 5129589..41656a0 100644
--- a/lips/data.lua
+++ b/lips/data.lua
@@ -29,13 +29,19 @@ data.fpu_registers = {
 }
 
 data.all_directives = {
-    'ALIGN', 'SKIP',
+    'ORG', 'ALIGN', 'SKIP',
     'ASCII', 'ASCIIZ',
-    'BYTE', 'HALFWORD', 'WORD', 'FLOAT',
+    'BYTE', 'HALFWORD', 'WORD',
     --'HEX', -- excluded here due to different syntax
     'INC', 'INCASM', 'INCLUDE',
     'INCBIN',
-    'ORG',
+    -- these are unlikely to be implemented
+    'FLOAT', 'DOUBLE',
+}
+
+data.directive_aliases = {
+    SPACE = 'SKIP',
+    HALF = 'HALFWORD',
 }
 
 data.all_registers = {}