diff --git a/driver/iverilog.man.in b/driver/iverilog.man.in
index ba05d2a0a..f8425713a 100644
--- a/driver/iverilog.man.in
+++ b/driver/iverilog.man.in
@@ -310,8 +310,8 @@ after a \fB\-Wall\fP argument to suppress isolated warning types.
 
 .TP 8
 .B all
-This enables the anachronisms, implicit, portbind, select\-range,
-timescale, and sensitivity\-entire\-array warning categories.
+This enables the anachronisms, implicit, macro-redefinition, portbind,
+select\-range, timescale, and sensitivity\-entire\-array warning categories.
 
 .TP 8
 .B anachronisms
@@ -324,6 +324,10 @@ This enables warnings for creation of implicit declarations. For
 example, if a scalar wire X is used but not declared in the Verilog
 source, this will print a warning at its first use.
 
+.TP 8
+.B macro-redefinition
+This enables preprocessor warnings when a macro is being redefined.
+
 .TP 8
 .B portbind
 This enables warnings for ports of module instantiations that are not