diff --git a/src/LanguageServer.php b/src/LanguageServer.php
index dc2d0a5c..7884f5af 100644
--- a/src/LanguageServer.php
+++ b/src/LanguageServer.php
@@ -307,6 +307,9 @@ public function initialize(ClientCapabilities $capabilities, string $rootPath =
             $serverCapabilities->xworkspaceReferencesProvider = true;
             $serverCapabilities->xdefinitionProvider = true;
             $serverCapabilities->xdependenciesProvider = true;
+            $serverCapabilities->experimental = [
+                'xevaluatableExpressionProvider' => true,
+            ];
 
             return new InitializeResult($serverCapabilities);
         });
diff --git a/src/Server/TextDocument.php b/src/Server/TextDocument.php
index 8f78c6f1..13bb82c5 100644
--- a/src/Server/TextDocument.php
+++ b/src/Server/TextDocument.php
@@ -426,4 +426,34 @@ public function xdefinition(TextDocumentIdentifier $textDocument, Position $posi
             return [new SymbolLocationInformation($descriptor, $def->symbolInformation->location)];
         });
     }
+
+    /**
+     * Return an evaluatable exrpession under the cursor for the debugger.
+     *
+     * @param TextDocumentIdentifier $textDocument The text document
+     * @param Position $position The position inside the text document
+     * @return Promise <EE>
+     */
+    public function xevaluatableExpression(TextDocumentIdentifier $textDocument, Position $position): Promise
+    {
+        return coroutine(function () use ($textDocument, $position) {
+            $document = yield $this->documentLoader->getOrLoad($textDocument->uri);
+            // Find the node under the cursor
+            $node = $document->getNodeAtPosition($position);
+            if ($node === null) {
+                return null;
+            }
+            if (
+                $node instanceof Node\Expression\Variable ||
+                $node instanceof Node\Parameter ||
+                $node instanceof Node\Expression\SubscriptExpression ||
+                $node instanceof Node\Expression\MemberAccessExpression ||
+                (($node2 = $node->getFirstAncestor(Node\Expression\SubscriptExpression::class)) && ($node = $node2))
+            ) {
+                $range = RangeFactory::fromNode($node);
+                return [ 'expression' => $node->getText(), 'range' => $range ];
+            }
+            return null;
+        });
+    }
 }
diff --git a/tests/LanguageServerTest.php b/tests/LanguageServerTest.php
index eef1a629..67b9f3fc 100644
--- a/tests/LanguageServerTest.php
+++ b/tests/LanguageServerTest.php
@@ -47,6 +47,9 @@ public function testInitialize()
         $serverCapabilities->xworkspaceReferencesProvider = true;
         $serverCapabilities->xdefinitionProvider = true;
         $serverCapabilities->xdependenciesProvider = true;
+        $serverCapabilities->experimental = [
+            'xevaluatableExpressionProvider' => true,
+        ];
 
         $this->assertEquals(new InitializeResult($serverCapabilities), $result);
     }