diff --git a/driver/cflexor.lex b/driver/cflexor.lex
index 3f3e46e80..c6e3eb860 100644
--- a/driver/cflexor.lex
+++ b/driver/cflexor.lex
@@ -4,7 +4,7 @@
 
 %{
 /*
- * Copyright (c) 2001-2016 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2001-2017 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -252,7 +252,7 @@ void destroy_lexor(void)
 {
 # ifdef FLEX_SCANNER
 #   if YY_FLEX_MAJOR_VERSION >= 2 && YY_FLEX_MINOR_VERSION >= 5
-#     if defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
+#     if YY_FLEX_MINOR_VERSION > 5 || defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
     yylex_destroy();
 #     endif
 #   endif
diff --git a/ivlpp/lexor.lex b/ivlpp/lexor.lex
index 626c7071c..8a4355264 100644
--- a/ivlpp/lexor.lex
+++ b/ivlpp/lexor.lex
@@ -2119,7 +2119,7 @@ void destroy_lexor(void)
 {
 # ifdef FLEX_SCANNER
 #   if YY_FLEX_MAJOR_VERSION >= 2 && YY_FLEX_MINOR_VERSION >= 5
-#     if defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
+#     if YY_FLEX_MINOR_VERSION > 5 || defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
     yylex_destroy();
 #     endif
 #   endif
diff --git a/lexor.lex b/lexor.lex
index 70fc1fda9..50d8c6ab9 100644
--- a/lexor.lex
+++ b/lexor.lex
@@ -1628,7 +1628,7 @@ void destroy_lexor()
 {
 # ifdef FLEX_SCANNER
 #   if YY_FLEX_MAJOR_VERSION >= 2 && YY_FLEX_MINOR_VERSION >= 5
-#     if defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
+#     if YY_FLEX_MINOR_VERSION > 5 || defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
     yylex_destroy();
 #     endif
 #   endif
diff --git a/tgt-pcb/fp.lex b/tgt-pcb/fp.lex
index af3292252..3536f51ae 100644
--- a/tgt-pcb/fp.lex
+++ b/tgt-pcb/fp.lex
@@ -6,7 +6,7 @@
 
 %{
 /*
- *  Copyright (C) 2011-2013 Stephen Williams (steve@icarus.com)
+ *  Copyright (C) 2011-2017 Stephen Williams (steve@icarus.com)
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -79,11 +79,14 @@ void init_fp_lexor(FILE*fd)
       yyrestart(fd);
 }
 
+/*
+ * Modern version of flex (>=2.5.9) can clean up the scanner data.
+ */
 void destroy_fp_lexor()
 {
 # ifdef FLEX_SCANNER
 #   if YY_FLEX_MAJOR_VERSION >= 2 && YY_FLEX_MINOR_VERSION >= 5
-#     if defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
+#     if YY_FLEX_MINOR_VERSION > 5 || defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
       yylex_destroy();
 #     endif
 #   endif
diff --git a/vhdlpp/lexor.lex b/vhdlpp/lexor.lex
index 8dd8d823a..fdafcb058 100644
--- a/vhdlpp/lexor.lex
+++ b/vhdlpp/lexor.lex
@@ -6,7 +6,7 @@
 
 %{
 /*
- * Copyright (c) 2011 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2011-2017 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -748,7 +748,16 @@ yyscan_t prepare_lexor(FILE*fd)
       return scanner;
 }
 
+/*
+ * Modern version of flex (>=2.5.9) can clean up the scanner data.
+ */
 void destroy_lexor(yyscan_t scanner)
 {
+# ifdef FLEX_SCANNER
+#   if YY_FLEX_MAJOR_VERSION >= 2 && YY_FLEX_MINOR_VERSION >= 5
+#     if YY_FLEX_MINOR_VERSION > 5 || defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
       yylex_destroy(scanner);
+#     endif
+#   endif
+# endif
 }
diff --git a/vpi/sdf_lexor.lex b/vpi/sdf_lexor.lex
index 0b8c7767e..9f05dd230 100644
--- a/vpi/sdf_lexor.lex
+++ b/vpi/sdf_lexor.lex
@@ -5,7 +5,7 @@
 
 %{
 /*
- * Copyright (c) 2007-2014 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2007-2017 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -217,7 +217,7 @@ static void destroy_sdf_lexor(void)
 {
 # ifdef FLEX_SCANNER
 #   if YY_FLEX_MAJOR_VERSION >= 2 && YY_FLEX_MINOR_VERSION >= 5
-#     if defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
+#     if YY_FLEX_MINOR_VERSION > 5 || defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
     yylex_destroy();
 #     endif
 #   endif
diff --git a/vpi/sys_readmem_lex.lex b/vpi/sys_readmem_lex.lex
index 22e5b0e80..c7f4c53ef 100644
--- a/vpi/sys_readmem_lex.lex
+++ b/vpi/sys_readmem_lex.lex
@@ -4,7 +4,7 @@
 
 %{
 /*
- * Copyright (c) 1999-2009 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 1999-2017 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -199,7 +199,7 @@ void destroy_readmem_lexor(void)
 {
 # ifdef FLEX_SCANNER
 #   if YY_FLEX_MAJOR_VERSION >= 2 && YY_FLEX_MINOR_VERSION >= 5
-#     if defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
+#     if YY_FLEX_MINOR_VERSION > 5 || defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
     yylex_destroy();
 #     endif
 #   endif
diff --git a/vpi/table_mod_lexor.lex b/vpi/table_mod_lexor.lex
index bd518ee7e..36031821b 100644
--- a/vpi/table_mod_lexor.lex
+++ b/vpi/table_mod_lexor.lex
@@ -6,7 +6,7 @@
 
 %{
 /*
- *  Copyright (C) 2011-2013  Cary R. (cygcary@yahoo.com)
+ *  Copyright (C) 2011-2017  Cary R. (cygcary@yahoo.com)
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -154,7 +154,7 @@ void destroy_tblmod_lexor(void)
 {
 # ifdef FLEX_SCANNER
 #   if YY_FLEX_MAJOR_VERSION >= 2 && YY_FLEX_MINOR_VERSION >= 5
-#     if defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
+#     if YY_FLEX_MINOR_VERSION > 5 || defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
     yylex_destroy();
 #     endif
 #   endif
diff --git a/vvp/lexor.lex b/vvp/lexor.lex
index b048ee612..3969c296d 100644
--- a/vvp/lexor.lex
+++ b/vvp/lexor.lex
@@ -4,7 +4,7 @@
 
 %{
 /*
- * Copyright (c) 2001-2016 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2001-2017 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -333,7 +333,7 @@ void destroy_lexor()
 {
 # ifdef FLEX_SCANNER
 #   if YY_FLEX_MAJOR_VERSION >= 2 && YY_FLEX_MINOR_VERSION >= 5
-#     if defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
+#     if YY_FLEX_MINOR_VERSION > 5 || defined(YY_FLEX_SUBMINOR_VERSION) && YY_FLEX_SUBMINOR_VERSION >= 9
     yylex_destroy();
 #     endif
 #   endif