diff --git a/service/dap/daptest/client.go b/service/dap/daptest/client.go
index e2390c8f..61d6c687 100644
--- a/service/dap/daptest/client.go
+++ b/service/dap/daptest/client.go
@@ -346,6 +346,13 @@ func (c *Client) InitializeRequest() {
 	c.send(request)
 }
 
+// InitializeRequestWithArgs sends an 'initialize' request with specified arguments.
+func (c *Client) InitializeRequestWithArgs(args dap.InitializeRequestArguments) {
+	request := &dap.InitializeRequest{Request: *c.newRequest("initialize")}
+	request.Arguments = args
+	c.send(request)
+}
+
 // LaunchRequest sends a 'launch' request with the specified args.
 func (c *Client) LaunchRequest(mode, program string, stopOnEntry bool) {
 	request := &dap.LaunchRequest{Request: *c.newRequest("launch")}
diff --git a/service/dap/error_ids.go b/service/dap/error_ids.go
index 68a4d3de..9cab0bcb 100644
--- a/service/dap/error_ids.go
+++ b/service/dap/error_ids.go
@@ -12,6 +12,7 @@ const (
 	// values below are inspired the original vscode-go debug adaptor.
 	FailedToLaunch             = 3000
 	FailedToAttach             = 3001
+	FailedToInitialize         = 3002
 	UnableToSetBreakpoints     = 2002
 	UnableToDisplayThreads     = 2003
 	UnableToProduceStackTrace  = 2004
diff --git a/service/dap/server.go b/service/dap/server.go
index d786a35a..3a15538d 100644
--- a/service/dap/server.go
+++ b/service/dap/server.go
@@ -608,6 +608,22 @@ func (s *Server) logToConsole(msg string) {
 }
 
 func (s *Server) onInitializeRequest(request *dap.InitializeRequest) {
+	if request.Arguments.PathFormat != "path" {
+		s.sendErrorResponse(request.Request, FailedToInitialize, "Failed to initialize",
+			fmt.Sprintf("Unsupported 'pathFormat' value '%s'.", request.Arguments.PathFormat))
+		return
+	}
+	if !request.Arguments.LinesStartAt1 {
+		s.sendErrorResponse(request.Request, FailedToInitialize, "Failed to initialize",
+			"Only 1-based line numbers are supported.")
+		return
+	}
+	if !request.Arguments.ColumnsStartAt1 {
+		s.sendErrorResponse(request.Request, FailedToInitialize, "Failed to initialize",
+			"Only 1-based column numbers are supported.")
+		return
+	}
+
 	// TODO(polina): Respond with an error if debug session is in progress?
 	response := &dap.InitializeResponse{Response: *newResponse(request.Request)}
 	response.Body.SupportsConfigurationDoneRequest = true
diff --git a/service/dap/server_test.go b/service/dap/server_test.go
index 65e011ad..7504b8da 100644
--- a/service/dap/server_test.go
+++ b/service/dap/server_test.go
@@ -50,6 +50,16 @@ func runTest(t *testing.T, name string, test func(c *daptest.Client, f protest.F
 	var buildFlags protest.BuildFlags = protest.AllNonOptimized
 	fixture := protest.BuildFixture(name, buildFlags)
 
+	// Start the DAP server.
+	client := startDapServer(t)
+	// client.Close will close the client connectinon, which will cause a connection error
+	// on the server side and signal disconnect to unblock Stop() above.
+	defer client.Close()
+
+	test(client, fixture)
+}
+
+func startDapServer(t *testing.T) *daptest.Client {
 	// Start the DAP server.
 	listener, err := net.Listen("tcp", ":0")
 	if err != nil {
@@ -76,11 +86,7 @@ func runTest(t *testing.T, name string, test func(c *daptest.Client, f protest.F
 	}()
 
 	client := daptest.NewClient(listener.Addr().String())
-	// This will close the client connectinon, which will cause a connection error
-	// on the server side and signal disconnect to unblock Stop() above.
-	defer client.Close()
-
-	test(client, fixture)
+	return client
 }
 
 // TestLaunchStopOnEntry emulates the message exchange that can be observed with
@@ -3337,6 +3343,66 @@ func TestBadAttachRequest(t *testing.T) {
 	})
 }
 
+func TestBadInitializeRequest(t *testing.T) {
+	runInitializeTest := func(args dap.InitializeRequestArguments, err string) {
+		t.Helper()
+		// Only one initialize request is allowed, so use a new server
+		// for each test.
+		client := startDapServer(t)
+		// client.Close will close the client connectinon, which will cause a connection error
+		// on the server side and signal disconnect to unblock Stop() above.
+		defer client.Close()
+
+		client.InitializeRequestWithArgs(args)
+		response := client.ExpectErrorResponse(t)
+		if response.Command != "initialize" {
+			t.Errorf("Command got %q, want \"launch\"", response.Command)
+		}
+		if response.Message != "Failed to initialize" {
+			t.Errorf("Message got %q, want \"Failed to launch\"", response.Message)
+		}
+		if response.Body.Error.Id != 3002 {
+			t.Errorf("Id got %d, want 3002", response.Body.Error.Id)
+		}
+		if response.Body.Error.Format != err {
+			t.Errorf("\ngot  %q\nwant %q", response.Body.Error.Format, err)
+		}
+	}
+
+	// Bad path format.
+	runInitializeTest(dap.InitializeRequestArguments{
+		AdapterID:       "go",
+		PathFormat:      "url", // unsupported 'pathFormat'
+		LinesStartAt1:   true,
+		ColumnsStartAt1: true,
+		Locale:          "en-us",
+	},
+		"Failed to initialize: Unsupported 'pathFormat' value 'url'.",
+	)
+
+	// LinesStartAt1 must be true.
+	runInitializeTest(dap.InitializeRequestArguments{
+		AdapterID:       "go",
+		PathFormat:      "path",
+		LinesStartAt1:   false, // only 1-based line numbers are supported
+		ColumnsStartAt1: true,
+		Locale:          "en-us",
+	},
+		"Failed to initialize: Only 1-based line numbers are supported.",
+	)
+
+	// ColumnsStartAt1 must be true.
+	runInitializeTest(dap.InitializeRequestArguments{
+		AdapterID:       "go",
+		PathFormat:      "path",
+		LinesStartAt1:   true,
+		ColumnsStartAt1: false, // only 1-based column numbers are supported
+		Locale:          "en-us",
+	},
+		"Failed to initialize: Only 1-based column numbers are supported.",
+	)
+}
+
 func TestBadlyFormattedMessageToServer(t *testing.T) {
 	runTest(t, "increment", func(client *daptest.Client, fixture protest.Fixture) {
 		// Send a badly formatted message to the server, and expect it to close the