diff --git a/source/maths/NUSpline.cpp b/source/maths/NUSpline.cpp
index a92aff050a..47fbdae55d 100644
--- a/source/maths/NUSpline.cpp
+++ b/source/maths/NUSpline.cpp
@@ -247,6 +247,8 @@ void TNSpline::RemoveNode(const int index)
 	if (m_NodeCount == 0 || index > m_NodeCount - 1)
 		return;
 
+	if (index > 0)
+		std::swap(m_Nodes[index].Distance, m_Nodes[index - 1].Distance);
 	m_MaxDistance -= m_Nodes[index].Distance;
 	m_Nodes.erase(m_Nodes.begin() + index);
 	--m_NodeCount;
diff --git a/source/maths/tests/test_NUSpline.h b/source/maths/tests/test_NUSpline.h
new file mode 100644
index 0000000000..c99baaaa00
--- /dev/null
+++ b/source/maths/tests/test_NUSpline.h
@@ -0,0 +1,120 @@
+/* Copyright (C) 2026 Wildfire Games.
+ * This file is part of 0 A.D.
+ *
+ * 0 A.D. is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 0 A.D. is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "lib/self_test.h"
+
+#include "maths/Fixed.h"
+#include "maths/NUSpline.h"
+
+#define TS_ASSERT_VEC_EQUALS(v, x, y, z) \
+	TS_ASSERT_EQUALS(v.X, x); \
+	TS_ASSERT_EQUALS(v.Y, y); \
+	TS_ASSERT_EQUALS(v.Z, z);
+
+class TestNUSpline : public CxxTest::TestSuite
+{
+public:
+	void test_TNSAddNode()
+	{
+		TNSpline spline{};
+		CFixedVector3D p0{fixed::FromInt(0), fixed::FromInt(0), fixed::FromInt(0)};
+		CFixedVector3D r0{fixed::FromInt(1), fixed::FromInt(1), fixed::FromInt(1)};
+		fixed d0 = fixed::FromInt(33);
+
+		CFixedVector3D p1{fixed::FromInt(1), fixed::FromInt(1), fixed::FromInt(1)};
+		CFixedVector3D r1{fixed::FromInt(2), fixed::FromInt(2), fixed::FromInt(2)};
+		fixed d1 = fixed::FromInt(4);
+
+		CFixedVector3D p2{fixed::FromInt(2), fixed::FromInt(2), fixed::FromInt(2)};
+		CFixedVector3D r2{fixed::FromInt(3), fixed::FromInt(3), fixed::FromInt(3)};
+		fixed d2 = fixed::FromInt(12);
+
+		spline.AddNode(p0, r0, d0);
+		spline.AddNode(p1, r1, d1);
+		spline.AddNode(p2, r2, d2);
+
+		TS_ASSERT_VEC_EQUALS(spline.GetPosition(0.f), 0, 0, 0);
+		TS_ASSERT_VEC_EQUALS(spline.GetPosition(0.25f), 1, 1, 1);
+		TS_ASSERT_VEC_EQUALS(spline.GetPosition(1.f), 2, 2, 2);
+
+		TS_ASSERT_EQUALS(spline.GetMaxDistance(), fixed::FromInt(16));
+	}
+
+	void test_TNSInsertNode()
+	{
+		TNSpline spline{};
+		CFixedVector3D p0{fixed::FromInt(0), fixed::FromInt(0), fixed::FromInt(0)};
+		CFixedVector3D r0{fixed::FromInt(1), fixed::FromInt(1), fixed::FromInt(1)};
+		fixed d0 = fixed::FromInt(4);
+
+		CFixedVector3D p1{fixed::FromInt(1), fixed::FromInt(1), fixed::FromInt(1)};
+		CFixedVector3D r1{fixed::FromInt(2), fixed::FromInt(2), fixed::FromInt(2)};
+		fixed d1 = fixed::FromInt(33);
+
+		CFixedVector3D p2{fixed::FromInt(2), fixed::FromInt(2), fixed::FromInt(2)};
+		CFixedVector3D r2{fixed::FromInt(3), fixed::FromInt(3), fixed::FromInt(3)};
+		fixed d2 = fixed::FromInt(12);
+
+		spline.InsertNode(0, p1, r1, d1);
+		spline.InsertNode(0, p0, r0, d0);
+		spline.InsertNode(2, p2, r2, d2);
+
+		TS_ASSERT_VEC_EQUALS(spline.GetPosition(0.f), 0, 0, 0);
+		TS_ASSERT_VEC_EQUALS(spline.GetPosition(0.25f), 1, 1, 1);
+		TS_ASSERT_VEC_EQUALS(spline.GetPosition(1.f), 2, 2, 2);
+
+		TS_ASSERT_EQUALS(spline.GetMaxDistance(), fixed::FromInt(16));
+	}
+
+	void test_TNSRemoveNode()
+	{
+		TNSpline spline{};
+		CFixedVector3D p0{fixed::FromInt(0), fixed::FromInt(0), fixed::FromInt(0)};
+		CFixedVector3D r0{fixed::FromInt(1), fixed::FromInt(1), fixed::FromInt(1)};
+		fixed d0 = fixed::FromInt(33);
+
+		CFixedVector3D p1{fixed::FromInt(1), fixed::FromInt(1), fixed::FromInt(1)};
+		CFixedVector3D r1{fixed::FromInt(2), fixed::FromInt(2), fixed::FromInt(2)};
+		fixed d1 = fixed::FromInt(4);
+
+		CFixedVector3D p2{fixed::FromInt(2), fixed::FromInt(2), fixed::FromInt(2)};
+		CFixedVector3D r2{fixed::FromInt(3), fixed::FromInt(3), fixed::FromInt(3)};
+		fixed d2 = fixed::FromInt(12);
+
+		spline.AddNode(p0, r0, d0);
+		spline.AddNode(p1, r1, d1);
+		spline.AddNode(p2, r2, d2);
+
+		spline.RemoveNode(2);
+
+		TS_ASSERT_VEC_EQUALS(spline.GetPosition(0.f), 0, 0, 0);
+		TS_ASSERT_VEC_EQUALS(spline.GetPosition(1.f), 1, 1, 1);
+
+		TS_ASSERT_EQUALS(spline.GetMaxDistance(), fixed::FromInt(4));
+
+		spline.RemoveNode(0);
+
+		TS_ASSERT_EQUALS(spline.GetMaxDistance(), fixed::FromInt(0));
+
+		spline.AddNode(p2, r2, d2);
+
+		TS_ASSERT_VEC_EQUALS(spline.GetPosition(0.f), 1, 1, 1);
+		TS_ASSERT_VEC_EQUALS(spline.GetPosition(1.f), 2, 2, 2);
+
+		TS_ASSERT_EQUALS(spline.GetMaxDistance(), fixed::FromInt(12));
+	}
+};