diff --git a/platformio.ini b/platformio.ini
index e422212..b8c2ee3 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -64,7 +64,12 @@ extends = esp32
 board = esp32dev
 build_type = debug
 board_build.partitions = esp32_3MB.csv
-build_flags = ${dualcore.build_flags}
+; -Og only limits inlining in units over large-unit-insns (10000 by default).
+; Smaller files inline ArduinoJson's helpers into every caller, which costs
+; KBs of flash per file, so treat every file as large.
+build_flags =
+	${dualcore.build_flags}
+	--param=large-unit-insns=1000
 
 [env:esp32c3]
 extends = esp32