diff --git a/driver/iverilog.man.in b/driver/iverilog.man.in
index 1850542f3..b36689f9e 100644
--- a/driver/iverilog.man.in
+++ b/driver/iverilog.man.in
@@ -1,4 +1,4 @@
-.TH iverilog 1 "Aug 10th, 2020" "" "Version %M.%n%E"
+.TH iverilog 1 "Jan 14th, 2021" "" "Version %M.%n%E"
 .SH NAME
 iverilog - Icarus Verilog compiler
 
@@ -582,9 +582,13 @@ The following macros are predefined by the compiler:
 .B __ICARUS__ = 1
 This is always defined when compiling with Icarus Verilog.
 
+.TP 8
+.B __ICARUS_SYNTH__ = 1
+This is defined when synthesis is enabled.
+
 .TP 8
 .B __VAMS_ENABLE__ = 1
-This is defined if Verilog\-AMS is enabled.
+This is defined when Verilog\-AMS is enabled.
 
 .SH ENVIRONMENT
 .PP
@@ -633,7 +637,7 @@ Tips on using, debugging, and developing the compiler can be found at
 
 .SH COPYRIGHT
 .nf
-Copyright \(co  2002\-2020 Stephen Williams
+Copyright \(co  2002\-2021 Stephen Williams
 
 This document can be freely redistributed according to the terms of the
 GNU General Public License version 2.0
diff --git a/driver/main.c b/driver/main.c
index 61f905bee..e1d6bead7 100644
--- a/driver/main.c
+++ b/driver/main.c
@@ -1116,8 +1116,6 @@ int main(int argc, char **argv)
       }
 
       fprintf(defines_file, "D:__ICARUS__=1\n");
-      if (strcmp(gen_verilog_ams,"verilog-ams") == 0)
-	    fprintf(defines_file, "D:__VAMS_ENABLE__=1\n");
 
 	/* Create another temporary file for passing configuration
 	   information to ivl. */
@@ -1301,6 +1299,11 @@ int main(int argc, char **argv)
 	    }
       }
 
+      if (strcmp(gen_verilog_ams,"verilog-ams") == 0)
+	    fprintf(defines_file, "D:__VAMS_ENABLE__=1\n");
+      if (synth_flag)
+	    fprintf(defines_file, "D:__ICARUS_SYNTH__=1\n");
+
       if (vpi_dir == 0)
 	    vpi_dir = base;
       if (ivlpp_dir == 0)