diff --git a/scripts/gen_gpio_defaults.py b/scripts/gen_gpio_defaults.py
index a4e9dc65..940c6e83 100755
--- a/scripts/gen_gpio_defaults.py
+++ b/scripts/gen_gpio_defaults.py
@@ -221,14 +221,24 @@ def usage():
             print('No configuration specified for GPIO ' + str(i) + '; skipping.')
             continue
 
+        valid_value = r"^13'h[0-9a-fA-F]{4}$"
+        value_match = re.match(valid_value, config_value)
+        if not value_match:
+            print('Error:  Default value ' + config_value + ' is not a 4-digit hex number; skipping')
+            continue
+
         try:
             default_str = config_value[-4:]
             binval = '{:013b}'.format(int(default_str, 16))
+            if len(binval) > 13:
+                print('Error:  Default value ' + config_value + ' is not a 4-digit hex number; skipping')
+                continue
+                
         except:
             print('Error:  Default value ' + config_value + ' is not a 4-digit hex number; skipping')
             continue
 
-        cell_name = 'gpio_defaults_block_' + default_str
+        cell_name = 'gpio_defaults_block_' + default_str.lower()
         mag_file = magpath + '/' + cell_name + '.mag'
         cellsused[i] = cell_name