diff --git a/.travis.yml b/.travis.yml
index 9240617..8639971 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,11 +1,16 @@
 matrix:
   include:
+    - os: osx
+      osx_image: xcode9.2
+      env: SWIFT_VERSION=4.0.3
     - os: osx
       osx_image: xcode9.4
       env: SWIFT_VERSION=4.1
     - os: osx
       osx_image: xcode10
       env: SWIFT_VERSION=4.2
+    - os: linux
+      env: SWIFT_VERSION=4.0.3
     - os: linux
       env: SWIFT_VERSION=4.1
     - os: linux
diff --git a/Package.swift b/Package.swift
index 2dd6977..b5fb304 100644
--- a/Package.swift
+++ b/Package.swift
@@ -1,4 +1,4 @@
-// swift-tools-version:4.1
+// swift-tools-version:4.0
 import PackageDescription
 
 let package = Package(
diff --git a/Sources/Errors.swift b/Sources/Errors.swift
index a6191f9..e885ab3 100644
--- a/Sources/Errors.swift
+++ b/Sources/Errors.swift
@@ -37,6 +37,15 @@ public struct TemplateSyntaxError : Error, Equatable, CustomStringConvertible {
   public init(_ description: String) {
     self.init(reason: description)
   }
+    
+  public static func ==(lhs: TemplateSyntaxError, rhs: TemplateSyntaxError) -> Bool {
+    return lhs.reason == rhs.reason &&
+    lhs.description == rhs.description &&
+    lhs.token == rhs.token &&
+    lhs.stackTrace == rhs.stackTrace &&
+    lhs.templateName == rhs.templateName &&
+    lhs.allTokens == rhs.allTokens
+  }
 }
 
 extension Error {
diff --git a/Sources/IfTag.swift b/Sources/IfTag.swift
index 125f55f..4fd6974 100644
--- a/Sources/IfTag.swift
+++ b/Sources/IfTag.swift
@@ -118,7 +118,12 @@ final class IfExpressionParser {
   private init(components: ArraySlice<String>, tokenParser: TokenParser, token: Token) throws {
     var parsedComponents = Set<Int>()
     var bracketsBalance = 0
-    self.tokens = try zip(components.indices, components).compactMap { (index, component) in
+    #if swift(>=4.1)
+    self.tokens = try zip(components.indices, components).compactMap { try parseComponent(index: $0.0, component: $0.1) }
+    #else
+    self.tokens = try zip(components.indices, components).flatMap { try parseComponent(index: $0.0, component: $0.1) }
+    #endif
+    func parseComponent(index: Int, component: String) throws -> IfToken? {
       guard !parsedComponents.contains(index) else { return nil }
 
       if component == "(" {
diff --git a/Sources/Inheritence.swift b/Sources/Inheritence.swift
index e512bfb..1507f1f 100644
--- a/Sources/Inheritence.swift
+++ b/Sources/Inheritence.swift
@@ -63,9 +63,11 @@ class ExtendsNode : NodeType {
     guard (parsedNodes.any { $0 is ExtendsNode }) == nil else {
       throw TemplateSyntaxError("'extends' cannot appear more than once in the same template")
     }
-
-    let blockNodes = parsedNodes.compactMap { $0 as? BlockNode }
-
+    #if swift(>=4.1)
+        let blockNodes = parsedNodes.compactMap { $0 as? BlockNode }
+    #else
+        let blockNodes = parsedNodes.flatMap { $0 as? BlockNode }
+    #endif
     let nodes = blockNodes.reduce([String: BlockNode]()) { (accumulator, node) -> [String: BlockNode] in
       var dict = accumulator
       dict[node.name] = node
diff --git a/Sources/Lexer.swift b/Sources/Lexer.swift
index f6fc426..77e956a 100644
--- a/Sources/Lexer.swift
+++ b/Sources/Lexer.swift
@@ -22,11 +22,17 @@ struct Lexer {
   init(templateName: String? = nil, templateString: String) {
     self.templateName = templateName
     self.templateString = templateString
-
-    self.lines = templateString.components(separatedBy: .newlines).enumerated().compactMap {
-      guard !$0.element.isEmpty else { return nil }
-      return (content: $0.element, number: UInt($0.offset + 1), templateString.range(of: $0.element)!)
-    }
+    #if swift(>=4.1)
+      self.lines = templateString.components(separatedBy: .newlines).enumerated().compactMap {
+        guard !$0.element.isEmpty else { return nil }
+        return (content: $0.element, number: UInt($0.offset + 1), templateString.range(of: $0.element)!)
+      }
+    #else
+      self.lines = templateString.components(separatedBy: .newlines).enumerated().flatMap {
+        guard !$0.element.isEmpty else { return nil }
+        return (content: $0.element, number: UInt($0.offset + 1), templateString.range(of: $0.element)!)
+      }
+    #endif
   }
 
   /// Create a token that will be passed on to the parser, with the given
diff --git a/Sources/Variable.swift b/Sources/Variable.swift
index eb30060..203ecc8 100644
--- a/Sources/Variable.swift
+++ b/Sources/Variable.swift
@@ -116,9 +116,32 @@ public struct Variable : Equatable, Resolvable {
 
     return normalize(current)
   }
+    
+  public static func ==(lhs: Variable, rhs: Variable) -> Bool {
+    return lhs.variable == rhs.variable
+  }
 }
 
+#if swift(>=4.1)
 private func resolveCollection<T: Collection>(_ collection: T, bit: String) -> Any? {
+  if let index = Int(bit) {
+    if index >= 0 && index < collection.count {
+        return collection[collection.index(collection.startIndex, offsetBy: index)]
+    } else {
+      return nil
+    }
+  } else if bit == "first" {
+    return collection.first
+  } else if bit == "last" {
+    return collection[collection.index(collection.endIndex, offsetBy: -1)]
+  } else if bit == "count" {
+    return collection.count
+  } else {
+    return nil
+  }
+}
+#else
+private func resolveCollection<T: Collection>(_ collection: T, bit: String) -> Any? where T.IndexDistance == Int {
   if let index = Int(bit) {
     if index >= 0 && index < collection.count {
       return collection[collection.index(collection.startIndex, offsetBy: index)]
@@ -135,6 +158,7 @@ private func resolveCollection<T: Collection>(_ collection: T, bit: String) -> A
     return nil
   }
 }
+#endif
 
 /// A structure used to represet range of two integer values expressed as `from...to`.
 /// Values should be numbers (they will be converted to integers).