diff --git a/include/mbedtls/bn_mul.h b/include/mbedtls/bn_mul.h
index 7b8019c..188d7f3 100644
--- a/include/mbedtls/bn_mul.h
+++ b/include/mbedtls/bn_mul.h
@@ -42,6 +42,10 @@
 
 #if defined(MBEDTLS_HAVE_ASM)
 
+#ifndef asm
+#define asm __asm
+#endif
+
 #if defined(__GNUC__)
 #if defined(__i386__)