diff --git a/annotation/src/main/java/lcsb/mapviewer/annotation/services/ChemicalParser.java b/annotation/src/main/java/lcsb/mapviewer/annotation/services/ChemicalParser.java
index 0ecb5a69cd2729897edb9741d978deb14881ee49..3277764f58a03729c44ad921320a83136cd15b86 100644
--- a/annotation/src/main/java/lcsb/mapviewer/annotation/services/ChemicalParser.java
+++ b/annotation/src/main/java/lcsb/mapviewer/annotation/services/ChemicalParser.java
@@ -70,7 +70,7 @@ public class ChemicalParser extends CachableInterface implements IExternalServic
   /**
    * Home page of ctd database.
    */
-  static final String URL = "http://ctdbase.org/";
+  static final String URL = "https://ctdbase.org/";
 
   /**
    * URL to get a list of chemicals by disease id.