diff --git a/src/sys/graphics/objgfx30.cpp b/src/sys/graphics/objgfx30.cpp
index 8798eb1..f3d10c8 100755
--- a/src/sys/graphics/objgfx30.cpp
+++ b/src/sys/graphics/objgfx30.cpp
@@ -124,12 +124,12 @@
         "pushl	%%eax             \n"
         "movb	(%%esi), %%al     \n"
         "incl	%%esi             \n"
-        "subb	%0, %%al          \n"
+        "subb	%1, %%al          \n"
         "popl	%%eax             \n"
         "decl	%%ecx             \n"
         "jcxz	lop               \n"
         :
-        :"S"(pal), "a"(red) 
+        :"S"(pal), "g"(red) 
         :"eax","ecx"
        ); // asm
     break;