diff --git a/lang/m2/comp/BigPars b/lang/m2/comp/BigPars
index 83a31229..5bc98601 100644
--- a/lang/m2/comp/BigPars
+++ b/lang/m2/comp/BigPars
@@ -94,6 +94,6 @@
 
 
 !File: uns_arith.h
-#define UNSIGNED_ARITH	unsigned arith
+#undef UNSIGNED_ARITH	unsigned arith
 
 
diff --git a/lang/m2/comp/SmallPars b/lang/m2/comp/SmallPars
index a062066d..fc774139 100644
--- a/lang/m2/comp/SmallPars
+++ b/lang/m2/comp/SmallPars
@@ -93,6 +93,6 @@
 
 
 !File: uns_arith.h
-#define UNSIGNED_ARITH	unsigned arith
+#undef UNSIGNED_ARITH	unsigned arith