diff --git a/libcxxabi/src/demangle/DemangleConfig.h b/libcxxabi/src/demangle/DemangleConfig.h
--- a/libcxxabi/src/demangle/DemangleConfig.h
+++ b/libcxxabi/src/demangle/DemangleConfig.h
@@ -11,11 +11,14 @@
 #ifndef LIBCXXABI_DEMANGLE_DEMANGLE_CONFIG_H
 #define LIBCXXABI_DEMANGLE_DEMANGLE_CONFIG_H
 
-// Must be defined before pulling in headers from libc++.
+// Must be defined before pulling in headers from libc++. Allow downstream
+// build systems to override this value.
 // https://libcxx.llvm.org/UsingLibcxx.html#enabling-the-safe-libc-mode
+#ifndef _LIBCPP_VERBOSE_ABORT
 #define _LIBCPP_VERBOSE_ABORT(...) abort_message(__VA_ARGS__)
-
 #include "../abort_message.h"
+#endif
+
 #include <ciso646>
 
 #ifdef _MSC_VER