diff --git a/libc/malloc_debug/Config.h b/libc/malloc_debug/Config.h
index 3bcef0b..86d1ee4 100644
--- a/libc/malloc_debug/Config.h
+++ b/libc/malloc_debug/Config.h
@@ -43,6 +43,7 @@
 constexpr uint64_t TRACK_ALLOCS = 0x80;
 constexpr uint64_t LEAK_TRACK = 0x100;
 constexpr uint64_t RECORD_ALLOCS = 0x200;
+constexpr uint64_t BACKTRACE_FULL = 0x400;
 
 // In order to guarantee posix compliance, set the minimum alignment
 // to 8 bytes for 32 bit systems and 16 bytes for 64 bit systems.