diff --git a/reactos/tools/widl/widl.c b/reactos/tools/widl/widl.c
index 07f024cea1d..00762f42dec 100644
--- a/reactos/tools/widl/widl.c
+++ b/reactos/tools/widl/widl.c
@@ -174,7 +174,7 @@ static char *make_token(const char *name)
   token = xstrdup(name);
   for (i=0; token[i]; i++) {
     if (!isalnum(token[i])) token[i] = '_';
-    else token[i] = toupper(token[i]);
+    else token[i] = tolower(token[i]);
   }
   return token;
 }
@@ -561,8 +561,8 @@ int main(int argc,char *argv[])
     fprintf(header, "/*** Autogenerated by WIDL %s from %s - Do not edit ***/\n", PACKAGE_VERSION, input_name);
     fprintf(header, "#include <rpc.h>\n" );
     fprintf(header, "#include <rpcndr.h>\n\n" );
-    fprintf(header, "#ifndef __WIDL_%s\n", header_token);
-    fprintf(header, "#define __WIDL_%s\n", header_token);
+    fprintf(header, "#ifndef __%s__\n", header_token);
+    fprintf(header, "#define __%s__\n", header_token);
     start_cplusplus_guard(header);
   }
 
@@ -606,7 +606,7 @@ int main(int argc,char *argv[])
     fprintf(header, "/* End additional prototypes */\n");
     fprintf(header, "\n");
     end_cplusplus_guard(header);
-    fprintf(header, "#endif /* __WIDL_%s */\n", header_token);
+    fprintf(header, "#endif /* __%s__ */\n", header_token);
     fclose(header);
   }
 
diff --git a/reactos/tools/widl/widl_ros.diff b/reactos/tools/widl/widl_ros.diff
index 1a92d7f8069..84aff9839cd 100644
--- a/reactos/tools/widl/widl_ros.diff
+++ b/reactos/tools/widl/widl_ros.diff
@@ -60,6 +60,38 @@ Index: typelib.c
  
  #include "widl.h"
  #include "utils.h"
+Index: widl.c
+===================================================================
+--- widl.c	(revision 32187)
++++ widl.c	(working copy)
+@@ -174,7 +174,7 @@
+   token = xstrdup(name);
+   for (i=0; token[i]; i++) {
+     if (!isalnum(token[i])) token[i] = '_';
+-    else token[i] = toupper(token[i]);
++    else token[i] = tolower(token[i]);
+   }
+   return token;
+ }
+@@ -561,8 +561,8 @@
+     fprintf(header, "/*** Autogenerated by WIDL %s from %s - Do not edit ***/\n", PACKAGE_VERSION, input_name);
+     fprintf(header, "#include <rpc.h>\n" );
+     fprintf(header, "#include <rpcndr.h>\n\n" );
+-    fprintf(header, "#ifndef __WIDL_%s\n", header_token);
+-    fprintf(header, "#define __WIDL_%s\n", header_token);
++    fprintf(header, "#ifndef __%s__\n", header_token);
++    fprintf(header, "#define __%s__\n", header_token);
+     start_cplusplus_guard(header);
+   }
+
+@@ -606,7 +606,7 @@
+     fprintf(header, "/* End additional prototypes */\n");
+     fprintf(header, "\n");
+     end_cplusplus_guard(header);
+-    fprintf(header, "#endif /* __WIDL_%s */\n", header_token);
++    fprintf(header, "#endif /* __%s__ */\n", header_token);
+     fclose(header);
+   }
 Index: widltypes.h
 ===================================================================
 --- widltypes.h	(revision 32187)