diff --git a/buildengine/build.go b/buildengine/build.go
index 43ec874cab..0705f23302 100644
--- a/buildengine/build.go
+++ b/buildengine/build.go
@@ -34,8 +34,8 @@ func buildModule(ctx context.Context, sch *schema.Schema, module Module, filesTr
 	logger := log.FromContext(ctx).Scope(module.Module)
 	ctx = log.ContextWithLogger(ctx, logger)
 
-	// clear stale module errors before extracting schema
-	if err := os.RemoveAll(filepath.Join(module.AbsDeployDir(), module.Errors)); err != nil {
+	// clear the deploy directory before extracting schema
+	if err := os.RemoveAll(module.AbsDeployDir()); err != nil {
 		return fmt.Errorf("failed to clear errors: %w", err)
 	}
 
diff --git a/buildengine/build_go_test.go b/buildengine/build_go_test.go
index eda40c6967..f3c4a58f0b 100644
--- a/buildengine/build_go_test.go
+++ b/buildengine/build_go_test.go
@@ -155,6 +155,21 @@ func Nothing(context.Context) error {
 	})
 }
 
+func TestGoBuildClearsBuildDir(t *testing.T) {
+	sch := &schema.Schema{
+		Modules: []*schema.Module{
+			schema.Builtins(),
+			{Name: "test"},
+		},
+	}
+	bctx := buildContext{
+		moduleDir: "testdata/projects/another",
+		buildDir:  "_ftl",
+		sch:       sch,
+	}
+	testBuildClearsBuildDir(t, bctx)
+}
+
 func TestMetadataImportsExcluded(t *testing.T) {
 	sch := &schema.Schema{
 		Modules: []*schema.Module{
diff --git a/buildengine/build_kotlin_test.go b/buildengine/build_kotlin_test.go
index f84aa01967..83217582fb 100644
--- a/buildengine/build_kotlin_test.go
+++ b/buildengine/build_kotlin_test.go
@@ -32,6 +32,21 @@ package ftl.test
 	})
 }
 
+func TestKotlinBuildClearsBuildDir(t *testing.T) {
+	sch := &schema.Schema{
+		Modules: []*schema.Module{
+			schema.Builtins(),
+			{Name: "test"},
+		},
+	}
+	bctx := buildContext{
+		moduleDir: "testdata/projects/echokotlin",
+		buildDir:  "target",
+		sch:       sch,
+	}
+	testBuildClearsBuildDir(t, bctx)
+}
+
 func TestGenerateAllTypes(t *testing.T) {
 	if testing.Short() {
 		t.SkipNow()
diff --git a/buildengine/build_test.go b/buildengine/build_test.go
index a417f61365..40655d9614 100644
--- a/buildengine/build_test.go
+++ b/buildengine/build_test.go
@@ -64,6 +64,35 @@ func testBuild(
 	assert.NoError(t, err, "Error removing build directory")
 }
 
+func testBuildClearsBuildDir(t *testing.T, bctx buildContext) {
+	t.Helper()
+	ctx := log.ContextWithLogger(context.Background(), log.Configure(os.Stderr, log.Config{}))
+	abs, err := filepath.Abs(bctx.moduleDir)
+	assert.NoError(t, err, "Error getting absolute path for module directory")
+
+	// build to generate the build directory
+	module, err := LoadModule(abs)
+	assert.NoError(t, err)
+	err = Build(ctx, bctx.sch, module, &mockModifyFilesTransaction{})
+	assert.NoError(t, err)
+
+	// create a temporary file in the build directory
+	buildDir := filepath.Join(bctx.moduleDir, bctx.buildDir)
+	tempFile, err := os.Create(filepath.Join(buildDir, "test-clear-build.tmp"))
+	assert.NoError(t, err, "Error creating temporary file in module directory")
+	tempFile.Close()
+
+	// build to clear the old build directory
+	module, err = LoadModule(abs)
+	assert.NoError(t, err)
+	err = Build(ctx, bctx.sch, module, &mockModifyFilesTransaction{})
+	assert.NoError(t, err)
+
+	// ensure the temporary file was removed
+	_, err = os.Stat(filepath.Join(buildDir, "test-clear-build.tmp"))
+	assert.Error(t, err, "Build directory was not removed")
+}
+
 func assertGeneratedModule(generatedModulePath string, expectedContent string) assertion {
 	return func(t testing.TB, bctx buildContext) error {
 		t.Helper()