diff --git a/compiler/optimizing/code_generator_arm.h b/compiler/optimizing/code_generator_arm.h
index 5b4b375..953e733 100644
--- a/compiler/optimizing/code_generator_arm.h
+++ b/compiler/optimizing/code_generator_arm.h
@@ -32,6 +32,7 @@
 
 // Use a local definition to prevent copying mistakes.
 static constexpr size_t kArmWordSize = kArmPointerSize;
+static constexpr size_t kArmBitsPerWord = kArmWordSize * kBitsPerByte;
 
 static constexpr Register kParameterCoreRegisters[] = { R1, R2, R3 };
 static constexpr size_t kParameterCoreRegistersLength = arraysize(kParameterCoreRegisters);