diff --git a/src/cmd/ksh93/include/shell.h b/src/cmd/ksh93/include/shell.h
index 900df6145..4619838fa 100644
--- a/src/cmd/ksh93/include/shell.h
+++ b/src/cmd/ksh93/include/shell.h
@@ -37,18 +37,6 @@
 #   include	<nval.h>
 #endif /* _SH_PRIVATE */
 
-/*
- * This is a macro that can be used to silence "unused parameter" warnings from the compiler for
- * functions which need to accept parameters they do not use because they need to be compatible
- * with an interface.
- */
-#undef NOT_USED
-#define NOT_USED(expr)		\
-	do {			\
-		(void)(expr);	\
-	} while (0)
-
-
 /* options */
 typedef struct
 {
diff --git a/src/lib/libast/include/ast.h b/src/lib/libast/include/ast.h
index c4ca23b0c..00aa5fd80 100644
--- a/src/lib/libast/include/ast.h
+++ b/src/lib/libast/include/ast.h
@@ -228,7 +228,7 @@ typedef struct
 
 #if defined(__STDC__) || defined(__cplusplus) || defined(c_plusplus)
 #define NiL		0
-#define NoP(x)		(void)(x)
+#define NoP(x)		do (void)(x); while(0)	/* for silencing "unused parameter" warnings */
 #else
 #define NiL		((char*)0)
 #define NoP(x)		(&x,1)