diff --git a/source/endian.cpp b/source/endian.cpp
index 39ecbcc4..8c39f295 100644
--- a/source/endian.cpp
+++ b/source/endian.cpp
@@ -33,7 +33,9 @@ enum {
   I32_ENDIAN_BIG = 0x00010203ul,
 };
 
-// TODO(dneto): This relies on undefined behaviour. Fix that.
+// This constant value allows the detection of the host machine's endianness.
+// Accessing it through the "value" member is valid due to C++11 section 3.10
+// paragraph 10.
 static const union {
   unsigned char bytes[4];
   uint32_t value;
diff --git a/test/UnitSPIRV.h b/test/UnitSPIRV.h
index 15459155..808ad5eb 100644
--- a/test/UnitSPIRV.h
+++ b/test/UnitSPIRV.h
@@ -61,8 +61,6 @@ enum {
   I32_ENDIAN_BIG = 0x00010203ul,
 };
 
-// TODO(dneto): Using a union this way relies on undefined behaviour.
-// Replace this with uses of BitwiseCast from util/bitutils.h
 static const union {
   unsigned char bytes[4];
   uint32_t value;