diff --git a/UI/Debugger/ViewModels/AssemblerWindowViewModel.cs b/UI/Debugger/ViewModels/AssemblerWindowViewModel.cs
index 0cad7584..043e1bfa 100644
--- a/UI/Debugger/ViewModels/AssemblerWindowViewModel.cs
+++ b/UI/Debugger/ViewModels/AssemblerWindowViewModel.cs
@@ -97,7 +97,9 @@ namespace Mesen.Debugger.ViewModels
 			StartAddress = address;
 			Code = code;
 
-			_originalCode = DebugApi.GetMemoryValues(CpuType.ToMemoryType(), (uint)StartAddress, (uint)(StartAddress + OriginalByteCount - 1));
+			if(OriginalByteCount > 0) {
+				_originalCode = DebugApi.GetMemoryValues(CpuType.ToMemoryType(), (uint)StartAddress, (uint)(StartAddress + OriginalByteCount - 1));
+			}
 		}
 
 		private void UpdateAssembly(string code)
diff --git a/UI/Debugger/ViewModels/DisassemblyViewModel.cs b/UI/Debugger/ViewModels/DisassemblyViewModel.cs
index 91d35693..3b9812e0 100644
--- a/UI/Debugger/ViewModels/DisassemblyViewModel.cs
+++ b/UI/Debugger/ViewModels/DisassemblyViewModel.cs
@@ -393,7 +393,11 @@ namespace Mesen.Debugger.ViewModels
 				}
 			} while(i < SelectionEnd);
 
-			byteCount = endAddress - SelectionStart + 1;
+			if(SelectionStart <= endAddress) {
+				byteCount = endAddress - SelectionStart + 1;
+			} else {
+				byteCount = 0;
+			}
 
 			return sb.ToString();
 		}