diff --git a/scripts/assemble.py b/scripts/assemble.py
index 0ee13bc..e60bae3 100755
--- a/scripts/assemble.py
+++ b/scripts/assemble.py
@@ -34,8 +34,8 @@
             return False
     return True
 
-offset_re = re.compile(r"^#define FLASH_AREA_([0-9A-Z_]+)_OFFSET(_0)?\s+((0x)?[0-9a-fA-F]+)")
-size_re   = re.compile(r"^#define FLASH_AREA_([0-9A-Z_]+)_SIZE(_0)?\s+((0x)?[0-9a-fA-F]+)")
+offset_re = re.compile(r"^#define FLASH_AREA_([0-9A-Z_]+)_OFFSET(_0)?\s+(0x[0-9a-fA-F]+|[0-9]+)$")
+size_re   = re.compile(r"^#define FLASH_AREA_([0-9A-Z_]+)_SIZE(_0)?\s+(0x[0-9a-fA-F]+|[0-9]+)$")
 
 class Assembly():
     def __init__(self, output, bootdir):