diff --git a/tests/site_scons/platforms/avr/avr.py b/tests/site_scons/platforms/avr/avr.py
index 6272983..2b26ead 100644
--- a/tests/site_scons/platforms/avr/avr.py
+++ b/tests/site_scons/platforms/avr/avr.py
@@ -12,7 +12,8 @@
     env.Append(CFLAGS = "-mmcu=atmega1284 -Dmain=app_main -Os")
     env.Append(CXXFLAGS = "-mmcu=atmega1284 -Dmain=app_main -Os -Wno-type-limits")
     env.Append(CPPDEFINES = {'PB_CONVERT_DOUBLE_FLOAT': 1, 'UNITTESTS_SHORT_MSGS': 1,
-                             '__ASSERT_USE_STDERR': 1, 'FUZZTEST_BUFSIZE': 2048})
+                             '__ASSERT_USE_STDERR': 1, 'MAX_ALLOC_BYTES': 32768,
+                             'FUZZTEST_BUFSIZE': 2048})
     env.Append(LINKFLAGS = "-mmcu=atmega1284")
     env.Append(LINKFLAGS = "-Wl,-Map,build/avr.map")