diff --git a/server/src/main/java/org/elasticsearch/index/mapper/RootObjectMapper.java b/server/src/main/java/org/elasticsearch/index/mapper/RootObjectMapper.java
index cd3242e98a2d7..a724cbb5f1dec 100644
--- a/server/src/main/java/org/elasticsearch/index/mapper/RootObjectMapper.java
+++ b/server/src/main/java/org/elasticsearch/index/mapper/RootObjectMapper.java
@@ -168,6 +168,9 @@ protected boolean processField(RootObjectMapper.Builder builder, String fieldNam
                       }
                   ]
                 */
+                if (!(fieldNode instanceof List)) {
+                    throw new MapperParsingException("Dynamic template syntax error");
+                }
                 List<?> tmplNodes = (List<?>) fieldNode;
                 List<DynamicTemplate> templates = new ArrayList<>();
                 for (Object tmplNode : tmplNodes) {