diff --git a/internal/lsp/cache/session.go b/internal/lsp/cache/session.go
index 9e9be16623..90b023cc45 100644
--- a/internal/lsp/cache/session.go
+++ b/internal/lsp/cache/session.go
@@ -49,6 +49,9 @@ type overlay struct {
 	// sameContentOnDisk is true if a file has been saved on disk,
 	// and therefore does not need to be part of the overlay sent to go/packages.
 	sameContentOnDisk bool
+
+	// unchanged is true if a file has not yet been edited.
+	unchanged bool
 }
 
 func (s *session) Shutdown(ctx context.Context) {
@@ -249,7 +252,7 @@ func (s *session) GetFile(uri span.URI) source.FileHandle {
 	return s.Cache().GetFile(uri)
 }
 
-func (s *session) SetOverlay(uri span.URI, data []byte) {
+func (s *session) SetOverlay(uri span.URI, data []byte) bool {
 	s.overlayMu.Lock()
 	defer func() {
 		s.overlayMu.Unlock()
@@ -258,14 +261,20 @@ func (s *session) SetOverlay(uri span.URI, data []byte) {
 
 	if data == nil {
 		delete(s.overlays, uri)
-		return
+		return false
 	}
+
+	o := s.overlays[uri]
+	firstChange := o != nil && o.unchanged
+
 	s.overlays[uri] = &overlay{
-		session: s,
-		uri:     uri,
-		data:    data,
-		hash:    hashContents(data),
+		session:   s,
+		uri:       uri,
+		data:      data,
+		hash:      hashContents(data),
+		unchanged: o == nil,
 	}
+	return firstChange
 }
 
 // openOverlay adds the file content to the overlay.
@@ -277,10 +286,11 @@ func (s *session) openOverlay(ctx context.Context, uri span.URI, data []byte) {
 		s.filesWatchMap.Notify(uri)
 	}()
 	s.overlays[uri] = &overlay{
-		session: s,
-		uri:     uri,
-		data:    data,
-		hash:    hashContents(data),
+		session:   s,
+		uri:       uri,
+		data:      data,
+		hash:      hashContents(data),
+		unchanged: true,
 	}
 	_, hash, err := s.cache.GetFile(uri).Read(ctx)
 	if err != nil {
diff --git a/internal/lsp/cache/view.go b/internal/lsp/cache/view.go
index b42f2147bd..e4db451abe 100644
--- a/internal/lsp/cache/view.go
+++ b/internal/lsp/cache/view.go
@@ -328,7 +328,7 @@ func (v *view) buildBuiltinPkg(ctx context.Context) {
 }
 
 // SetContent sets the overlay contents for a file.
-func (v *view) SetContent(ctx context.Context, uri span.URI, content []byte) error {
+func (v *view) SetContent(ctx context.Context, uri span.URI, content []byte) (bool, error) {
 	v.mu.Lock()
 	defer v.mu.Unlock()
 
@@ -338,10 +338,9 @@ func (v *view) SetContent(ctx context.Context, uri span.URI, content []byte) err
 	v.backgroundCtx, v.cancel = context.WithCancel(v.baseCtx)
 
 	if !v.Ignore(uri) {
-		v.session.SetOverlay(uri, content)
+		return v.session.SetOverlay(uri, content), nil
 	}
-
-	return nil
+	return false, nil
 }
 
 // invalidateContent invalidates the content of a Go file,
diff --git a/internal/lsp/source/view.go b/internal/lsp/source/view.go
index 9c67bad2ca..3a0fb8f62c 100644
--- a/internal/lsp/source/view.go
+++ b/internal/lsp/source/view.go
@@ -188,7 +188,7 @@ type Session interface {
 	IsOpen(uri span.URI) bool
 
 	// Called to set the effective contents of a file from this session.
-	SetOverlay(uri span.URI, data []byte)
+	SetOverlay(uri span.URI, data []byte) (wasFirstChange bool)
 }
 
 // View represents a single workspace.
@@ -211,7 +211,7 @@ type View interface {
 	GetFile(ctx context.Context, uri span.URI) (File, error)
 
 	// Called to set the effective contents of a file from this view.
-	SetContent(ctx context.Context, uri span.URI, content []byte) error
+	SetContent(ctx context.Context, uri span.URI, content []byte) (wasFirstChange bool, err error)
 
 	// BackgroundContext returns a context used for all background processing
 	// on behalf of this view.
diff --git a/internal/lsp/text_synchronization.go b/internal/lsp/text_synchronization.go
index 17d28692c1..d90b041c9a 100644
--- a/internal/lsp/text_synchronization.go
+++ b/internal/lsp/text_synchronization.go
@@ -31,14 +31,6 @@ func (s *Server) didOpen(ctx context.Context, params *protocol.DidOpenTextDocume
 
 	view := s.session.ViewOf(uri)
 
-	// TODO: Ideally, we should be able to specify that a generated file should be opened as read-only.
-	if source.IsGenerated(ctx, view, uri) {
-		s.client.ShowMessage(ctx, &protocol.ShowMessageParams{
-			Message: fmt.Sprintf("Do not edit this file! %s is a generated file.", uri.Filename()),
-			Type:    protocol.Warning,
-		})
-	}
-
 	// Run diagnostics on the newly-changed file.
 	go func() {
 		ctx := view.BackgroundContext()
@@ -76,9 +68,20 @@ func (s *Server) didChange(ctx context.Context, params *protocol.DidChangeTextDo
 	}
 	// Cache the new file content and send fresh diagnostics.
 	view := s.session.ViewOf(uri)
-	if err := view.SetContent(ctx, uri, []byte(text)); err != nil {
+	wasFirstChange, err := view.SetContent(ctx, uri, []byte(text))
+	if err != nil {
 		return err
 	}
+
+	// TODO: Ideally, we should be able to specify that a generated file should be opened as read-only.
+	// Tell the user that they should not be editing a generated file.
+	if source.IsGenerated(ctx, view, uri) && wasFirstChange {
+		s.client.ShowMessage(ctx, &protocol.ShowMessageParams{
+			Message: fmt.Sprintf("Do not edit this file! %s is a generated file.", uri.Filename()),
+			Type:    protocol.Warning,
+		})
+	}
+
 	// Run diagnostics on the newly-changed file.
 	go func() {
 		ctx := view.BackgroundContext()
@@ -140,7 +143,7 @@ func (s *Server) didClose(ctx context.Context, params *protocol.DidCloseTextDocu
 	ctx = telemetry.File.With(ctx, uri)
 	s.session.DidClose(uri)
 	view := s.session.ViewOf(uri)
-	if err := view.SetContent(ctx, uri, nil); err != nil {
+	if _, err := view.SetContent(ctx, uri, nil); err != nil {
 		return err
 	}
 	clear := []span.URI{uri} // by default, clear the closed URI