diff --git a/ivlpp/globals.h b/ivlpp/globals.h
index 3c2b95865..623baa54a 100644
--- a/ivlpp/globals.h
+++ b/ivlpp/globals.h
@@ -22,6 +22,7 @@
 # include  <stdio.h>
 
 extern void reset_lexor(FILE*out, char*paths[]);
+extern void destroy_lexor();
 extern void load_precompiled_defines(FILE*src);
 extern void define_macro(const char*name, const char*value, int keyword,
                          int argc);
diff --git a/ivlpp/lexor.lex b/ivlpp/lexor.lex
index 6e780f69d..d0a086e2e 100644
--- a/ivlpp/lexor.lex
+++ b/ivlpp/lexor.lex
@@ -1803,3 +1803,17 @@ void reset_lexor(FILE* out, char* paths[])
         tail = isp;
     }
 }
+
+/*
+ * Modern version of flex (>=2.5.9) can clean up the scanner data.
+ */
+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
+    yylex_destroy();
+#     endif
+#   endif
+# endif
+}
diff --git a/ivlpp/main.c b/ivlpp/main.c
index af7e66719..a8d761ebc 100644
--- a/ivlpp/main.c
+++ b/ivlpp/main.c
@@ -370,6 +370,7 @@ int main(int argc, char*argv[])
 	   start scanning. */
       reset_lexor(out, source_list);
       if (yylex()) return -1;
+      destroy_lexor();
 
       if(depend_file) {
 	      fclose(depend_file);