diff --git a/src/crystalline/controller.cr b/src/crystalline/controller.cr
index 6e0ee82..a408fd5 100644
--- a/src/crystalline/controller.cr
+++ b/src/crystalline/controller.cr
@@ -76,7 +76,15 @@ class Crystalline::Controller
     when LSP::DocumentSymbolsRequest
       @documents_lock.synchronize do
         file_uri = URI.parse message.params.text_document.uri
-        workspace.document_symbols(@server, file_uri)
+        document_symbols = workspace.document_symbols(@server, file_uri)
+
+        if @server.client_capabilities.text_document.try &.document_symbol.try &.hierarchical_document_symbol_support
+          document_symbols
+        else
+          document_symbols.try &.reduce([] of LSP::SymbolInformation) { |acc, document_symbol|
+            acc.concat(document_symbol.to_symbol_information_array(message.params.text_document.uri))
+          }
+        end
       end
     else
       nil
diff --git a/src/crystalline/lsp/requests/language_features/document_symbols.cr b/src/crystalline/lsp/requests/language_features/document_symbols.cr
index 74bff10..2caf4ac 100644
--- a/src/crystalline/lsp/requests/language_features/document_symbols.cr
+++ b/src/crystalline/lsp/requests/language_features/document_symbols.cr
@@ -55,6 +55,31 @@ module LSP
 
     # Children of this symbol, e.g. properties of a class.
     property children : Array(DocumentSymbol)?
+
+    def to_symbol_information_array(uri : String)
+      results = [] of LSP::SymbolInformation
+      deque = Deque(Tuple(LSP::DocumentSymbol, LSP::DocumentSymbol?)){ {self, nil} }
+
+      loop do
+        break if deque.size == 0
+        symbol, parent = deque.shift
+        results << LSP::SymbolInformation.new(
+          name: symbol.name,
+          kind: symbol.kind,
+          deprecated: symbol.deprecated,
+          location: LSP::Location.new(
+            uri: uri,
+            range: symbol.range
+          ),
+          container_name: parent.try &.name
+        )
+        symbol.children.try { |children|
+          deque.concat(children.map { |c| {c, self} })
+        }
+      end
+
+      results
+    end
   end
 
   # Represents information about programming constructs like variables, classes,
@@ -67,7 +92,7 @@ module LSP
     property name : String
 
     # The kind of this symbol.
-    property kind : SymbolKind
+    property kind : LSP::SymbolKind
 
     # Indicates if this symbol is deprecated.
     property deprecated : Bool?
diff --git a/src/crystalline/lsp/server.cr b/src/crystalline/lsp/server.cr
index 9d26bad..1095e77 100644
--- a/src/crystalline/lsp/server.cr
+++ b/src/crystalline/lsp/server.cr
@@ -20,6 +20,8 @@ class LSP::Server
   getter output : IO
   # The broadcasted server capabilites.
   getter server_capabilities : LSP::ServerCapabilities
+  # The lsp client capabilites.
+  getter! client_capabilities : LSP::ClientCapabilities
   # A list of requests that were sent to clients to keep track of the ID and kind.
   getter requests_sent : Hash(RequestMessage::RequestId, LSP::Message) = {} of RequestMessage::RequestId => LSP::Message
   # Incremental.
@@ -126,6 +128,7 @@ class LSP::Server
     loop do
       initialize_message = self.class.read(@input)
       if initialize_message.is_a? LSP::InitializeRequest
+        @client_capabilities = initialize_message.params.capabilities
         if controller.responds_to? :on_init
           init_result = controller.on_init(initialize_message.params)
         else