diff --git a/app/src/main/java/com/vitorpamplona/amethyst/service/NIP30Parser.kt b/app/src/main/java/com/vitorpamplona/amethyst/service/NIP30Parser.kt
index 0bc315756..bfc14cf36 100644
--- a/app/src/main/java/com/vitorpamplona/amethyst/service/NIP30Parser.kt
+++ b/app/src/main/java/com/vitorpamplona/amethyst/service/NIP30Parser.kt
@@ -6,6 +6,8 @@ class NIP30Parser {
     val customEmojiPattern: Pattern = Pattern.compile("\\:([A-Za-z0-9_\\-]+)\\:", Pattern.CASE_INSENSITIVE)
 
     fun buildArray(input: String): List<String> {
+        checkNotInMainThread()
+
         val matcher = customEmojiPattern.matcher(input)
         val list = mutableListOf<String>()
         while (matcher.find()) {