diff --git a/gdb-port/parser.py b/gdb-port/parser.py
index 0d0e9941a729a981f692ecb01614b803703e5d01..cbdd8c9397824cea264a652ccbf34b4d37baefd9 100644
--- a/gdb-port/parser.py
+++ b/gdb-port/parser.py
@@ -22,10 +22,7 @@ class Parser:
 
 	# 'arena' is expected to be int, and size probably should be too
 	def add_mem_use(self, arena, size):
-		if self.bytes_used.setdefault(arena, None) is None:
-			self.bytes_used[arena] = size
-		else:
-			self.bytes_used[arena] += size
+		self.bytes_used[arena] = self.bytes_used.get(arena, 0) + size
 
 	# 'arena' is expected to be int
 	def get_mem_use(self, arena=None):