diff --git a/internal/api/runners.go b/internal/api/runners.go
index 9ed4a6e..ca411e6 100644
--- a/internal/api/runners.go
+++ b/internal/api/runners.go
@@ -8,6 +8,7 @@ import (
 	"github.com/openHPI/poseidon/internal/config"
 	"github.com/openHPI/poseidon/internal/runner"
 	"github.com/openHPI/poseidon/pkg/dto"
+	"io"
 	"net/http"
 	"net/url"
 )
@@ -131,6 +132,12 @@ func (r *RunnerController) findRunnerMiddleware(next http.Handler) http.Handler
 		runnerID := mux.Vars(request)[RunnerIDKey]
 		targetRunner, err := r.manager.Get(runnerID)
 		if err != nil {
+			// We discard the request body because an early write causes errors for some clients.
+			// See https://github.com/openHPI/poseidon/issues/54
+			_, readErr := io.ReadAll(request.Body)
+			if readErr != nil {
+				log.WithError(readErr).Warn("Failed to discard the request body")
+			}
 			writeNotFound(writer, err)
 			return
 		}
diff --git a/internal/api/runners_test.go b/internal/api/runners_test.go
index 2f6c5f0..5e06a26 100644
--- a/internal/api/runners_test.go
+++ b/internal/api/runners_test.go
@@ -17,6 +17,8 @@ import (
 	"testing"
 )
 
+const invalidID = "some-invalid-runner-id"
+
 type MiddlewareTestSuite struct {
 	suite.Suite
 	manager        *runner.ManagerMock
@@ -67,7 +69,6 @@ func (s *MiddlewareTestSuite) TestFindRunnerMiddlewareIfRunnerExists() {
 }
 
 func (s *MiddlewareTestSuite) TestFindRunnerMiddlewareIfRunnerDoesNotExist() {
-	invalidID := "some-invalid-runner-id"
 	s.manager.On("Get", invalidID).Return(nil, runner.ErrRunnerNotFound)
 
 	recorder := httptest.NewRecorder()
@@ -76,6 +77,22 @@ func (s *MiddlewareTestSuite) TestFindRunnerMiddlewareIfRunnerDoesNotExist() {
 	s.Equal(http.StatusNotFound, recorder.Code)
 }
 
+func (s *MiddlewareTestSuite) TestFindRunnerMiddlewareDoesNotEarlyRespond() {
+	body := strings.NewReader(strings.Repeat("A", 798968))
+
+	path, err := s.router.Get("test-runner-id").URL(RunnerIDKey, invalidID)
+	s.Require().NoError(err)
+	request, err := http.NewRequest(http.MethodPost, path.String(), body)
+	s.Require().NoError(err)
+
+	s.manager.On("Get", mock.AnythingOfType("string")).Return(nil, runner.ErrRunnerNotFound)
+	recorder := httptest.NewRecorder()
+	s.router.ServeHTTP(recorder, request)
+
+	s.Equal(http.StatusNotFound, recorder.Code)
+	s.Equal(0, body.Len()) // No data should be unread
+}
+
 func TestRunnerRouteTestSuite(t *testing.T) {
 	suite.Run(t, new(RunnerRouteTestSuite))
 }
@@ -261,7 +278,6 @@ func (s *UpdateFileSystemRouteTestSuite) TestUpdateFileSystemReturnsBadRequestOn
 }
 
 func (s *UpdateFileSystemRouteTestSuite) TestUpdateFileSystemToNonExistingRunnerReturnsNotFound() {
-	invalidID := "some-invalid-runner-id"
 	s.runnerManager.On("Get", invalidID).Return(nil, runner.ErrRunnerNotFound)
 	path, err := s.router.Get(UpdateFileSystemPath).URL(RunnerIDKey, invalidID)
 	s.Require().NoError(err)