diff --git a/app/ime.go b/app/ime.go
index df944da8..b60c9a21 100644
--- a/app/ime.go
+++ b/app/ime.go
@@ -5,6 +5,7 @@ package app
 import (
 	"unicode"
 	"unicode/utf16"
+	"unicode/utf8"
 
 	"gioui.org/io/input"
 	"gioui.org/io/key"
@@ -117,3 +118,28 @@ func (e *editorState) RunesIndex(chars int) int {
 	// Assume runes after snippets are one UTF-16 character each.
 	return runes + chars
 }
+
+// areSnippetsConsistent reports whether the content of the old snippet is
+// consistent with the content of the new.
+func areSnippetsConsistent(old, new key.Snippet) bool {
+	// Compute the overlapping range.
+	r := old.Range
+	r.Start = max(r.Start, new.Start)
+	r.End = max(r.End, r.Start)
+	r.End = min(r.End, new.End)
+	return snippetSubstring(old, r) == snippetSubstring(new, r)
+}
+
+func snippetSubstring(s key.Snippet, r key.Range) string {
+	for r.Start > s.Start && r.Start < s.End {
+		_, n := utf8.DecodeRuneInString(s.Text)
+		s.Text = s.Text[n:]
+		s.Start++
+	}
+	for r.End < s.End && r.End > s.Start {
+		_, n := utf8.DecodeLastRuneInString(s.Text)
+		s.Text = s.Text[:len(s.Text)-n]
+		s.End--
+	}
+	return s.Text
+}
diff --git a/app/os_macos.go b/app/os_macos.go
index 375ddb81..3a01ef25 100644
--- a/app/os_macos.go
+++ b/app/os_macos.go
@@ -534,7 +534,7 @@ func (w *window) SetCursor(cursor pointer.Cursor) {
 }
 
 func (w *window) EditorStateChanged(old, new editorState) {
-	if old.Selection.Range != new.Selection.Range || old.Snippet != new.Snippet {
+	if old.Selection.Range != new.Selection.Range || !areSnippetsConsistent(old.Snippet, new.Snippet) {
 		C.discardMarkedText(w.view)
 		w.w.SetComposingRegion(key.Range{Start: -1, End: -1})
 	}