diff --git a/lib/graph/graph.hpp b/lib/graph/graph.hpp
index c06331e..6d2f75b 100644
--- a/lib/graph/graph.hpp
+++ b/lib/graph/graph.hpp
@@ -198,20 +198,18 @@ inline void Graph<V>::modifyVertex(const_reference old_data, const_reference new
   if (old_data == new_data)
     return;
 
-  v_iterator it = m_vertices.find(old_data);
-  if (it == m_vertices.end())
-    return;
-
   std::vector<value_type> neighbours = neighboursOf(old_data);
   for (auto &v : neighbours) {
     std::vector<value_type>& n_v = nonConstNeighboursOf(v);
     typename std::vector<value_type>::iterator n_it = std::find(n_v.begin(), n_v.end(), old_data);
     *n_it = new_data;
   }
+  const auto number_of_removed_elements = m_vertices.erase(old_data);
 
-  m_vertices.erase(it);
-  std::pair<V, edge_container> p(new_data, neighbours);
-  m_vertices.insert(p);
+  if (number_of_removed_elements > 0) {
+    std::pair<V, edge_container> p(new_data, neighbours);
+    m_vertices.insert(p);
+  }
 }
 
 template <typename V>
diff --git a/test/graph/test_graph.hpp b/test/graph/test_graph.hpp
index 4f99470..c39da43 100644
--- a/test/graph/test_graph.hpp
+++ b/test/graph/test_graph.hpp
@@ -351,7 +351,7 @@ TEST_CASE( "Graph custom vertices", "[graph][data_structure]" ) {
 
 }
 
-TEST_CASE( "Graph adding/removing", "[graph][data_structure]" ) {
+TEST_CASE( "Graph adding/removing with more data", "[graph][data_structure]" ) {
 
   SECTION("Adding some edges") {
     Graph<int> g = { {1, 2}, {1, 3}, {1, 4}, {2, 4}, {3, 4} };
@@ -445,6 +445,48 @@ TEST_CASE( "Graph adding/removing", "[graph][data_structure]" ) {
     REQUIRE( connected(g, 4, 2) == true );
     REQUIRE( connected(g, 4, 3) == true );
   }
+
+  SECTION("Adding some edges, modifying 1 vertex") {
+    Graph<int> g = { {1, 2}, {1, 3}, {1, 4}, {2, 4}, {3, 4} };
+    REQUIRE( numberOfVertices(g) == 4 );
+    REQUIRE( numberOfEdges(g) == 5*2 );
+
+    g.modifyVertex(1, 5);
+    REQUIRE( numberOfVertices(g) == 4 );
+    REQUIRE( numberOfEdges(g) == 5*2 );
+    REQUIRE( contains(g, 1) == false );
+    REQUIRE( contains(g, 5) == true );
+
+    REQUIRE( connected(g, 1, 2) == false );
+    REQUIRE( connected(g, 1, 3) == false );
+    REQUIRE( connected(g, 1, 4) == false );
+    REQUIRE( connected(g, 2, 1) == false );
+    REQUIRE( connected(g, 2, 4) == true );
+    REQUIRE( connected(g, 3, 1) == false );
+    REQUIRE( connected(g, 3, 4) == true );
+    REQUIRE( connected(g, 4, 1) == false );
+    REQUIRE( connected(g, 4, 2) == true );
+    REQUIRE( connected(g, 4, 3) == true );
+
+    REQUIRE( connected(g, 5, 2) == true );
+    REQUIRE( connected(g, 5, 3) == true );
+    REQUIRE( connected(g, 5, 4) == true );
+    REQUIRE( connected(g, 2, 5) == true );
+    REQUIRE( connected(g, 3, 5) == true );
+    REQUIRE( connected(g, 4, 5) == true );
+  }
+
+  SECTION("Adding some edges, modifying 1 unexisting vertex") {
+    Graph<int> g = { {1, 2}, {1, 3}, {1, 4}, {2, 4}, {3, 4} };
+    REQUIRE( numberOfVertices(g) == 4 );
+    REQUIRE( numberOfEdges(g) == 5*2 );
+
+    g.modifyVertex(5, 6);
+    REQUIRE( numberOfVertices(g) == 4 );
+    REQUIRE( numberOfEdges(g) == 5*2 );
+    REQUIRE( contains(g, 5) == false );
+    REQUIRE( contains(g, 6) == false );
+  }
 }