diff --git a/libcxxabi/src/Unwind/assembly.h b/libcxxabi/src/Unwind/assembly.h
index b749d67167d6..f46a24d0eed9 100644
--- a/libcxxabi/src/Unwind/assembly.h
+++ b/libcxxabi/src/Unwind/assembly.h
@@ -62,6 +62,10 @@
   SYMBOL_NAME(name):
 
 #if defined(__arm__)
+#if !defined(__ARM_ARCH)
+#define __ARM_ARCH 4
+#endif
+
 #if defined(__ARM_ARCH_4T__) || __ARM_ARCH >= 5
 #define ARM_HAS_BX
 #endif