diff --git a/Sources/AsyncHTTPClient/HTTPHandler.swift b/Sources/AsyncHTTPClient/HTTPHandler.swift
index e835eeda7..678f5cc5a 100644
--- a/Sources/AsyncHTTPClient/HTTPHandler.swift
+++ b/Sources/AsyncHTTPClient/HTTPHandler.swift
@@ -385,14 +385,48 @@ extension HTTPClientResponseDelegate {
     public func didReceiveError(task: HTTPClient.Task<Response>, _: Error) {}
 }
 
-internal extension URL {
+extension URL {
+    var percentEncodedPath: String {
+        if self.path.isEmpty {
+            return "/"
+        }
+        return self.path.addingPercentEncoding(withAllowedCharacters: .urlPathAllowed) ?? self.path
+    }
+
+    var pathHasTrailingSlash: Bool {
+        if #available(OSX 10.11, iOS 9.0, tvOS 9.0, watchOS 2.0, *) {
+            return self.hasDirectoryPath
+        } else {
+            // Most platforms should use `self.hasDirectoryPath`, but on older darwin platforms
+            // we have this approximation instead.
+            let url = self.absoluteString
+
+            var pathEndIndex = url.index(before: url.endIndex)
+            if let queryIndex = url.firstIndex(of: "?") {
+                pathEndIndex = url.index(before: queryIndex)
+            } else if let fragmentIndex = url.suffix(from: url.firstIndex(of: "@") ?? url.startIndex).lastIndex(of: "#") {
+                pathEndIndex = url.index(before: fragmentIndex)
+            }
+
+            return url[pathEndIndex] == "/"
+        }
+    }
+
     var uri: String {
-        let urlEncodedPath = path.addingPercentEncoding(withAllowedCharacters: .urlPathAllowed) ?? path
-        return path.isEmpty ? "/" : urlEncodedPath + (query.map { "?" + $0 } ?? "")
+        var uri = self.percentEncodedPath
+        if self.pathHasTrailingSlash, uri != "/" {
+            uri += "/"
+        }
+
+        if let query = self.query {
+            uri += "?" + query
+        }
+
+        return uri
     }
 
     func hasTheSameOrigin(as other: URL) -> Bool {
-        return host == other.host && scheme == other.scheme && port == other.port
+        return self.host == other.host && self.scheme == other.scheme && self.port == other.port
     }
 }
 
diff --git a/Tests/AsyncHTTPClientTests/HTTPClientInternalTests+XCTest.swift b/Tests/AsyncHTTPClientTests/HTTPClientInternalTests+XCTest.swift
index 6ad239e02..ad172d12b 100644
--- a/Tests/AsyncHTTPClientTests/HTTPClientInternalTests+XCTest.swift
+++ b/Tests/AsyncHTTPClientTests/HTTPClientInternalTests+XCTest.swift
@@ -30,6 +30,7 @@ extension HTTPClientInternalTests {
             ("testProxyStreaming", testProxyStreaming),
             ("testProxyStreamingFailure", testProxyStreamingFailure),
             ("testUploadStreamingBackpressure", testUploadStreamingBackpressure),
+            ("testRequestURITrailingSlash", testRequestURITrailingSlash),
         ]
     }
 }
diff --git a/Tests/AsyncHTTPClientTests/HTTPClientInternalTests.swift b/Tests/AsyncHTTPClientTests/HTTPClientInternalTests.swift
index 6d73caf95..e17d0e871 100644
--- a/Tests/AsyncHTTPClientTests/HTTPClientInternalTests.swift
+++ b/Tests/AsyncHTTPClientTests/HTTPClientInternalTests.swift
@@ -193,4 +193,39 @@ class HTTPClientInternalTests: XCTestCase {
 
         XCTAssertEqual(delegate.reads, 3)
     }
+
+    func testRequestURITrailingSlash() throws {
+        let request1 = try Request(url: "https://someserver.com:8888/some/path?foo=bar#ref")
+        XCTAssertEqual(request1.url.uri, "/some/path?foo=bar")
+
+        let request2 = try Request(url: "https://someserver.com:8888/some/path/?foo=bar#ref")
+        XCTAssertEqual(request2.url.uri, "/some/path/?foo=bar")
+
+        let request3 = try Request(url: "https://someserver.com:8888?foo=bar#ref")
+        XCTAssertEqual(request3.url.uri, "/?foo=bar")
+
+        let request4 = try Request(url: "https://someserver.com:8888/?foo=bar#ref")
+        XCTAssertEqual(request4.url.uri, "/?foo=bar")
+
+        let request5 = try Request(url: "https://someserver.com:8888/some/path")
+        XCTAssertEqual(request5.url.uri, "/some/path")
+
+        let request6 = try Request(url: "https://someserver.com:8888/some/path/")
+        XCTAssertEqual(request6.url.uri, "/some/path/")
+
+        let request7 = try Request(url: "https://someserver.com:8888")
+        XCTAssertEqual(request7.url.uri, "/")
+
+        let request8 = try Request(url: "https://someserver.com:8888/")
+        XCTAssertEqual(request8.url.uri, "/")
+
+        let request9 = try Request(url: "https://someserver.com:8888#ref")
+        XCTAssertEqual(request9.url.uri, "/")
+
+        let request10 = try Request(url: "https://someserver.com:8888/#ref")
+        XCTAssertEqual(request10.url.uri, "/")
+
+        let request11 = try Request(url: "https://someserver.com/some%20path")
+        XCTAssertEqual(request11.url.uri, "/some%20path")
+    }
 }