diff --git a/src/SFML/Graphics/ConvexShape.cpp b/src/SFML/Graphics/ConvexShape.cpp
index 978862e2..da446ddc 100644
--- a/src/SFML/Graphics/ConvexShape.cpp
+++ b/src/SFML/Graphics/ConvexShape.cpp
@@ -27,6 +27,8 @@
 ////////////////////////////////////////////////////////////
 #include <SFML/Graphics/ConvexShape.hpp>
 
+#include <cassert>
+
 
 namespace sf
 {
@@ -55,6 +57,7 @@ std::size_t ConvexShape::getPointCount() const
 ////////////////////////////////////////////////////////////
 void ConvexShape::setPoint(std::size_t index, const Vector2f& point)
 {
+    assert(index < m_points.size() && "Index is out of bounds");
     m_points[index] = point;
     update();
 }
@@ -63,6 +66,7 @@ void ConvexShape::setPoint(std::size_t index, const Vector2f& point)
 ////////////////////////////////////////////////////////////
 Vector2f ConvexShape::getPoint(std::size_t index) const
 {
+    assert(index < m_points.size() && "Index is out of bounds");
     return m_points[index];
 }
 
diff --git a/src/SFML/Graphics/VertexArray.cpp b/src/SFML/Graphics/VertexArray.cpp
index 9067ec7a..027f2bee 100644
--- a/src/SFML/Graphics/VertexArray.cpp
+++ b/src/SFML/Graphics/VertexArray.cpp
@@ -28,6 +28,8 @@
 #include <SFML/Graphics/RenderTarget.hpp>
 #include <SFML/Graphics/VertexArray.hpp>
 
+#include <cassert>
+
 
 namespace sf
 {
@@ -51,6 +53,7 @@ std::size_t VertexArray::getVertexCount() const
 ////////////////////////////////////////////////////////////
 Vertex& VertexArray::operator[](std::size_t index)
 {
+    assert(index < m_vertices.size() && "Index is out of bounds");
     return m_vertices[index];
 }
 
@@ -58,6 +61,7 @@ Vertex& VertexArray::operator[](std::size_t index)
 ////////////////////////////////////////////////////////////
 const Vertex& VertexArray::operator[](std::size_t index) const
 {
+    assert(index < m_vertices.size() && "Index is out of bounds");
     return m_vertices[index];
 }
 
diff --git a/src/SFML/System/String.cpp b/src/SFML/System/String.cpp
index cf2d95ae..7de8eea6 100644
--- a/src/SFML/System/String.cpp
+++ b/src/SFML/System/String.cpp
@@ -31,6 +31,7 @@
 #include <iterator>
 #include <utility>
 
+#include <cassert>
 #include <cstring>
 
 
@@ -213,6 +214,7 @@ String& String::operator+=(const String& right)
 ////////////////////////////////////////////////////////////
 char32_t String::operator[](std::size_t index) const
 {
+    assert(index < m_string.size() && "Index is out of bounds");
     return m_string[index];
 }
 
@@ -220,6 +222,7 @@ char32_t String::operator[](std::size_t index) const
 ////////////////////////////////////////////////////////////
 char32_t& String::operator[](std::size_t index)
 {
+    assert(index < m_string.size() && "Index is out of bounds");
     return m_string[index];
 }