diff --git a/Source/include/mafianet/variable_list_delta_tracker.h b/Source/include/mafianet/variable_list_delta_tracker.h
index cc17d8f9c..0e73d2d86 100644
--- a/Source/include/mafianet/variable_list_delta_tracker.h
+++ b/Source/include/mafianet/variable_list_delta_tracker.h
@@ -56,8 +56,8 @@ class VariableListDeltaTracker
 			variableList[nextWriteIndex].lastData=(char*) rakRealloc_Ex(variableList[nextWriteIndex].lastData, temp.GetNumberOfBytesUsed(),_FILE_AND_LINE_);
 			variableList[nextWriteIndex].byteLength=temp.GetNumberOfBytesUsed();
 			memcpy(variableList[nextWriteIndex].lastData,temp.GetData(),temp.GetNumberOfBytesUsed());
-			nextWriteIndex++;
 			variableList[nextWriteIndex].isDirty=false;
+			nextWriteIndex++;
 			return true; // Different because the serialized size is different
 		}
 		if (variableList[nextWriteIndex].isDirty==false && memcmp(temp.GetData(),variableList[nextWriteIndex].lastData, variableList[nextWriteIndex].byteLength)==0)
diff --git a/Tests/Unit/VariableListDeltaTrackerTests.cpp b/Tests/Unit/VariableListDeltaTrackerTests.cpp
new file mode 100644
index 000000000..223560252
--- /dev/null
+++ b/Tests/Unit/VariableListDeltaTrackerTests.cpp
@@ -0,0 +1,77 @@
+/*
+ *  Copyright (c) 2026, MafiaHub
+ *
+ *  This source code is licensed under the MIT-style license found in the
+ *  license.txt file in the root directory of this source tree.
+ */
+
+#include <gtest/gtest.h>
+
+#include "mafianet/variable_list_delta_tracker.h"
+#include "mafianet/string.h"
+
+using namespace MafiaNet;
+
+namespace
+{
+	unsigned char DirtyBit(unsigned int index)
+	{
+		return static_cast<unsigned char>(0x80 >> (index & 7));
+	}
+}
+
+TEST(VariableListDeltaTracker, UnchangedValueIsNotWrittenAgain)
+{
+	VariableListDeltaTracker tracker;
+	tracker.StartWrite();
+	EXPECT_TRUE(tracker.WriteVar(RakString("a")));
+	tracker.StartWrite();
+	EXPECT_FALSE(tracker.WriteVar(RakString("a")));
+}
+
+TEST(VariableListDeltaTracker, ResizedValueKeepsTheNextVariableDirty)
+{
+	VariableListDeltaTracker tracker;
+	tracker.StartWrite();
+	tracker.WriteVar(RakString("a"));
+	tracker.WriteVar(5);
+
+	unsigned char dirty[1] = { DirtyBit(1) };
+	tracker.FlagDirtyFromBitArray(dirty);
+
+	tracker.StartWrite();
+	EXPECT_TRUE(tracker.WriteVar(RakString("abc")));
+	EXPECT_TRUE(tracker.WriteVar(5));
+}
+
+TEST(VariableListDeltaTracker, ResizedValueClearsItsOwnDirtyFlag)
+{
+	VariableListDeltaTracker tracker;
+	tracker.StartWrite();
+	tracker.WriteVar(RakString("a"));
+	tracker.WriteVar(5);
+
+	unsigned char dirty[1] = { DirtyBit(0) };
+	tracker.FlagDirtyFromBitArray(dirty);
+
+	tracker.StartWrite();
+	EXPECT_TRUE(tracker.WriteVar(RakString("abc")));
+	tracker.WriteVar(5);
+
+	tracker.StartWrite();
+	EXPECT_FALSE(tracker.WriteVar(RakString("abc")));
+}
+
+TEST(VariableListDeltaTracker, ResizingTheLastVariableStaysInBounds)
+{
+	VariableListDeltaTracker tracker;
+	tracker.StartWrite();
+	tracker.WriteVar(RakString("a"));
+
+	tracker.StartWrite();
+	EXPECT_TRUE(tracker.WriteVar(RakString("abc")));
+	EXPECT_TRUE(tracker.IsPastEndOfList());
+
+	tracker.StartWrite();
+	EXPECT_FALSE(tracker.WriteVar(RakString("abc")));
+}