diff --git a/libsrc/atari/mou/atrjoy.s b/libsrc/atari/mou/atrjoy.s
index e1c745adf..9915a4ff1 100644
--- a/libsrc/atari/mou/atrjoy.s
+++ b/libsrc/atari/mou/atrjoy.s
@@ -91,6 +91,8 @@ visible:        .res    1
 
 .rodata
 
+; (We use ".proc" because we want to define both a label and a scope.)
+
 .proc   DefVars
         .word   SCREEN_HEIGHT/2         ; YPos
         .word   SCREEN_WIDTH/2          ; XPos
diff --git a/libsrc/atari/mou/atrst.s b/libsrc/atari/mou/atrst.s
index 1e7e77b3a..72808ad16 100644
--- a/libsrc/atari/mou/atrst.s
+++ b/libsrc/atari/mou/atrst.s
@@ -113,6 +113,8 @@ oldval:         .res    1
 
 .rodata
 
+; (We use ".proc" because we want to define both a label and a scope.)
+
 .proc   DefVars
         .word   (SCREEN_HEIGHT+1)/2     ; YPos
         .word   (SCREEN_WIDTH+1)/2      ; XPos