diff --git a/src/utils/bit_reader.h b/src/utils/bit_reader.h
index 0fc62d33..ec3426cd 100644
--- a/src/utils/bit_reader.h
+++ b/src/utils/bit_reader.h
@@ -43,10 +43,12 @@ extern "C" {
 #define BITS 56
 #elif defined(__arm__) || defined(_M_ARM)      // ARM
 #define BITS 24
+#elif defined(__aarch64__)                     // ARM 64bit
+#define BITS 56
 #elif defined(__mips__)                        // MIPS
 #define BITS 24
 #else                                          // reasonable default
-#define BITS 24  // TODO(skal): test aarch64 and find the proper BITS value.
+#define BITS 24
 #endif
 
 //------------------------------------------------------------------------------