diff --git a/libs/grok/src/main/java/org/elasticsearch/grok/Grok.java b/libs/grok/src/main/java/org/elasticsearch/grok/Grok.java
index 1a87d1a4709dd..d383f79b23e2e 100644
--- a/libs/grok/src/main/java/org/elasticsearch/grok/Grok.java
+++ b/libs/grok/src/main/java/org/elasticsearch/grok/Grok.java
@@ -54,9 +54,7 @@ public final class Grok {
             "(?::(?<subname>[[:alnum:]@\\[\\]_:.-]+))?" +
             ")" +
             "(?:=(?<definition>" +
-            "(?:" +
             "(?:[^{}]+|\\.+)+" +
-            ")+" +
             ")" +
             ")?" + "\\}";
     private static final Regex GROK_PATTERN_REGEX = new Regex(GROK_PATTERN.getBytes(StandardCharsets.UTF_8), 0,