diff --git a/OSBindings/Mac/Clock SignalTests/WolfgangLorenzTests.swift b/OSBindings/Mac/Clock SignalTests/WolfgangLorenzTests.swift
index 7f9e6f7c1..a7233d8e4 100644
--- a/OSBindings/Mac/Clock SignalTests/WolfgangLorenzTests.swift	
+++ b/OSBindings/Mac/Clock SignalTests/WolfgangLorenzTests.swift	
@@ -256,6 +256,11 @@ class WolfgangLorenzTests: XCTestCase, CSTestMachineTrapHandler {
 				machine.setValue(0x0801, for: .programCounter)
 				machine.setValue(0xfd, for: .stackPointer)
 				machine.setValue(0x04, for: .flags)
+
+				// For consistency when debugging; otherwise immaterial.
+				machine.setValue(0x00, for: .A)
+				machine.setValue(0x00, for: .X)
+				machine.setValue(0x00, for: .Y)
 			}
 		}
 
diff --git a/Processors/65816/Implementation/65816Implementation.hpp b/Processors/65816/Implementation/65816Implementation.hpp
index d8b11676b..59ceebd56 100644
--- a/Processors/65816/Implementation/65816Implementation.hpp
+++ b/Processors/65816/Implementation/65816Implementation.hpp
@@ -249,7 +249,10 @@ template <typename BusHandler> void Processor<BusHandler>::run_for(const Cycles
 			continue;
 
 			case OperationConstructDirectIndexedIndirect:
-				data_address_ = data_bank_ + (direct_ + x() + instruction_buffer_.value) & 0xffff;
+				data_address_ = data_bank_ + (
+					((direct_ + x() + instruction_buffer_.value) & e_masks_[1]) +
+					(direct_ & e_masks_[0])
+				) & 0xffff;
 				if(!(direct_&0xff)) {
 					++next_op_;
 				}