diff --git a/utils/esxdos.def b/utils/esxdos.def
index 1621eda..2f712c4 100644
--- a/utils/esxdos.def
+++ b/utils/esxdos.def
@@ -7,6 +7,9 @@
 ; Compatible compilers:
 ;   SJAsmPlus, <https://github.com/sjasmplus/sjasmplus/>
 
+ ifndef esxdos_def_included
+ define esxdos_def_included
+
         define  FA_READ         0x01
         define  FA_WRITE        0x02
         define  FA_OPEN_AL      0x08
@@ -21,3 +24,5 @@
                 rst     $08
                 defb    dato
               endm
+
+ endif  ; !esxdos_def_included
diff --git a/utils/zxuno.def b/utils/zxuno.def
index 9f0b12a..f5faa92 100644
--- a/utils/zxuno.def
+++ b/utils/zxuno.def
@@ -7,6 +7,9 @@
 ; Compatible compilers:
 ;   SJAsmPlus, <https://github.com/sjasmplus/sjasmplus/>
 
+ ifndef zxuno_def_included
+ define zxuno_def_included
+
         define  zxuno_port      $fc3b
         define  master_conf     0
         define  master_mapper   1
@@ -44,3 +47,5 @@
                 call    rst28
                 defb    dir, dato
               endm
+
+ endif  ; !zxuno_def_included