diff --git a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
index 40eb0d36f1..89404b3ce0 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
+++ b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
@@ -2935,7 +2935,7 @@ Please run: Tools/scripts/build_bootloaders.py %s
             return False
         return True
 
-    def process_line(self, line):
+    def process_line(self, line, depth):
         '''process one line of pin definition file'''
         self.all_lines.append(line)
         a = shlex.split(line, posix=False)
@@ -3074,14 +3074,21 @@ Please run: Tools/scripts/build_bootloaders.py %s
             # extract numerical defines for processing by other parts of the script
             result = re.match(r'define\s*([A-Z_0-9]+)\s+([0-9]+)', line)
             if result:
-                self.intdefines[result.group(1)] = int(result.group(2))
+                (name, intvalue) = (result.group(1), int(result.group(2)))
+                if name in self.intdefines and self.intdefines[name] == intvalue:
+                    msg = f"{name} already in defines with same value"
+                    if depth == 0:
+                        print(msg)
+                        # raise ValueError(msg)
+
+                self.intdefines[name] = intvalue
 
     def progress(self, message):
         if self.quiet:
             return
         print(message)
 
-    def process_file(self, filename):
+    def process_file(self, filename, depth=0):
         '''process a hwdef.dat file'''
         try:
             f = open(filename, "r")
@@ -3100,9 +3107,9 @@ Please run: Tools/scripts/build_bootloaders.py %s
                     include_file = os.path.normpath(
                         os.path.join(dir, include_file))
                 self.progress("Including %s" % include_file)
-                self.process_file(include_file)
+                self.process_file(include_file, depth+1)
             else:
-                self.process_line(line)
+                self.process_line(line, depth)
 
     def add_apperiph_defaults(self, f):
         '''add default defines for peripherals'''