diff --git a/org.eclipse.wildwebdeveloper/META-INF/MANIFEST.MF b/org.eclipse.wildwebdeveloper/META-INF/MANIFEST.MF
index 1b607b3678..244554cef4 100644
--- a/org.eclipse.wildwebdeveloper/META-INF/MANIFEST.MF
+++ b/org.eclipse.wildwebdeveloper/META-INF/MANIFEST.MF
@@ -11,8 +11,8 @@ Bundle-Activator: org.eclipse.wildwebdeveloper.Activator
 Require-Bundle: org.eclipse.ui,
  org.eclipse.core.runtime;bundle-version="3.29.0",
  org.eclipse.lsp4e;bundle-version="0.18.9",
- org.eclipse.lsp4j.jsonrpc;bundle-version="0.12.0",
- org.eclipse.lsp4j;bundle-version="0.12.0",
+ org.eclipse.lsp4j.jsonrpc;bundle-version="1.0.0",
+ org.eclipse.lsp4j;bundle-version="1.0.0",
  org.eclipse.tm4e.registry;bundle-version="0.1.0",
  org.eclipse.ui.genericeditor;bundle-version="1.0.0",
  org.eclipse.tm4e.ui;bundle-version="0.1.0",
diff --git a/org.eclipse.wildwebdeveloper/src/org/eclipse/wildwebdeveloper/markdown/MarkdownDiagnosticsManager.java b/org.eclipse.wildwebdeveloper/src/org/eclipse/wildwebdeveloper/markdown/MarkdownDiagnosticsManager.java
index abd9a5d733..b6e8ca5123 100644
--- a/org.eclipse.wildwebdeveloper/src/org/eclipse/wildwebdeveloper/markdown/MarkdownDiagnosticsManager.java
+++ b/org.eclipse.wildwebdeveloper/src/org/eclipse/wildwebdeveloper/markdown/MarkdownDiagnosticsManager.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2025 Vegard IT GmbH and others.
+ * Copyright (c) 2025, 2026 Vegard IT GmbH and others.
  *
  * This program and the accompanying materials are made
  * available under the terms of the Eclipse Public License 2.0
@@ -52,6 +52,7 @@
 import org.eclipse.lsp4j.DocumentDiagnosticParams;
 import org.eclipse.lsp4j.DocumentDiagnosticReport;
 import org.eclipse.lsp4j.FullDocumentDiagnosticReport;
+import org.eclipse.lsp4j.MarkupContent;
 import org.eclipse.lsp4j.Range;
 import org.eclipse.lsp4j.RelatedFullDocumentDiagnosticReport;
 import org.eclipse.lsp4j.TextDocumentIdentifier;
@@ -248,7 +249,7 @@ private static synchronized void applyMarkers(final IFile file, final List<Diagn
 			}
 
 			for (final Diagnostic d : diagnostics) {
-				final String msg = d.getMessage();
+				final String msg = getMessageString(d);
 				final int severity = toIMarkerSeverity(d.getSeverity());
 				final int line = d.getRange() != null ? d.getRange().getStart().getLine() + 1 : 1;
 				int charStart = -1, charEnd = -1;
@@ -291,6 +292,15 @@ private static synchronized void applyMarkers(final IFile file, final List<Diagn
 		}
 	}
 
+	private static String getMessageString(final Diagnostic d) {
+		Either<String, MarkupContent> message = d.getMessage();
+		if (message.isLeft()) {
+			return message.getLeft();
+		} else {
+			return message.getRight().getValue();
+		}
+	}
+
 	private static void clearMarkers(final IFile file) throws CoreException {
 		file.deleteMarkers(MARKDOWN_MARKER_TYPE, true, IResource.DEPTH_ZERO);
 	}