diff --git a/Package.swift b/Package.swift
index ae05b8b..938d93e 100644
--- a/Package.swift
+++ b/Package.swift
@@ -1,4 +1,4 @@
-// swift-tools-version:4.2
+// swift-tools-version:5.0
 
 import PackageDescription
 
diff --git a/Sources/ElementaryCycles/Private/AdjacencyMatrix+getAdjacencyMatrix.swift b/Sources/ElementaryCycles/Private/AdjacencyMatrix+getAdjacencyMatrix.swift
index f077d64..c93f756 100644
--- a/Sources/ElementaryCycles/Private/AdjacencyMatrix+getAdjacencyMatrix.swift
+++ b/Sources/ElementaryCycles/Private/AdjacencyMatrix+getAdjacencyMatrix.swift
@@ -24,7 +24,7 @@ extension Matrix where Element == Bool {
         for (offset, node) in nodes.enumerated() {
             if let adjacentNodes = adjacencyDictionary[node] {
                 for adjacentNode in adjacentNodes {
-                    guard let adjacentIndex = nodes.index(of: adjacentNode) else {
+                    guard let adjacentIndex = nodes.firstIndex(of: adjacentNode) else {
                         throw Error.indexNotFound(node: adjacentNode, nodes: nodes)
                     }
                     matrix[offset][adjacentIndex] = true
diff --git a/Sources/ElementaryCyclesSearch/Public/ElementaryCyclesSearch.swift b/Sources/ElementaryCyclesSearch/Public/ElementaryCyclesSearch.swift
index 2a514d3..f4dd71a 100644
--- a/Sources/ElementaryCyclesSearch/Public/ElementaryCyclesSearch.swift
+++ b/Sources/ElementaryCyclesSearch/Public/ElementaryCyclesSearch.swift
@@ -168,7 +168,7 @@ public class ElementaryCyclesSearch<Node> {
             }
         }
 
-        if let index = stack.index(of: v) {
+        if let index = stack.firstIndex(of: v) {
             stack.remove(at: index)
         }
         return f
diff --git a/Sources/ElementaryCyclesSearch/Public/Vector/Vector.swift b/Sources/ElementaryCyclesSearch/Public/Vector/Vector.swift
index 8fecf85..e5da1f8 100644
--- a/Sources/ElementaryCyclesSearch/Public/Vector/Vector.swift
+++ b/Sources/ElementaryCyclesSearch/Public/Vector/Vector.swift
@@ -83,7 +83,7 @@ extension Vector where Element: Equatable {
     
     @discardableResult
     func remove(element: Element) -> Bool {
-        if let index = array.index(of: element) {
+        if let index = array.firstIndex(of: element) {
             array.remove(at: -index.distance(to: 0))
             return true
         }
diff --git a/Tests/ElementaryCyclesTests/AdjacencyMatrixShould.swift b/Tests/ElementaryCyclesTests/AdjacencyMatrixShould.swift
index abddd21..571e061 100644
--- a/Tests/ElementaryCyclesTests/AdjacencyMatrixShould.swift
+++ b/Tests/ElementaryCyclesTests/AdjacencyMatrixShould.swift
@@ -31,10 +31,10 @@ final class AdjacencyMatrixShould: XCTestCase {
                      "IT": ["FR"]]
         let nodes = AdjacencyMatrix.getNodes(graph: graph, sort: nil)
         let adjacencyMatrix = try! AdjacencyMatrix.getAdjacencyMatrix(nodes: nodes, adjacencyDictionary: graph)
-        let es = nodes.index(of: "ES")!
-        let pt = nodes.index(of: "PT")!
-        let fr = nodes.index(of: "FR")!
-        let it = nodes.index(of: "IT")!
+        let es = nodes.firstIndex(of: "ES")!
+        let pt = nodes.firstIndex(of: "PT")!
+        let fr = nodes.firstIndex(of: "FR")!
+        let it = nodes.firstIndex(of: "IT")!
         XCTAssertTrue(adjacencyMatrix[es][pt] ?? adjacencyMatrix[pt][es] ?? false)
         XCTAssertTrue(adjacencyMatrix[es][fr] ?? adjacencyMatrix[fr][es] ?? false)
         XCTAssertTrue(adjacencyMatrix[fr][it] ?? adjacencyMatrix[it][fr] ?? false)