diff --git a/icu4c/source/common/lstmbe.cpp b/icu4c/source/common/lstmbe.cpp
index b15b5e44..3bd88bb2 100644
--- a/icu4c/source/common/lstmbe.cpp
+++ b/icu4c/source/common/lstmbe.cpp
@@ -554,7 +554,7 @@ GraphemeClusterVectorizer::~GraphemeClusterVectorizer()
 {
 }
 
-constexpr int32_t MAX_GRAPHEME_CLSTER_LENGTH = 11;
+constexpr int32_t MAX_GRAPHEME_CLSTER_LENGTH = 20;
 
 void GraphemeClusterVectorizer::vectorize(
     UText *text, int32_t startPos, int32_t endPos,