diff --git a/src/main/java/org/verapdf/pd/font/cmap/CMap.java b/src/main/java/org/verapdf/pd/font/cmap/CMap.java
index 56dcdaa8..7a1cb1ce 100644
--- a/src/main/java/org/verapdf/pd/font/cmap/CMap.java
+++ b/src/main/java/org/verapdf/pd/font/cmap/CMap.java
@@ -166,6 +166,10 @@ public int getCodeFromStream(InputStream stream) throws IOException {
      * @param another is another CMap.
      */
     public void useCMap(CMap another) {
+        if (another == null) {
+            LOGGER.log(Level.WARNING, "The provided CMap is null. No data merged into the current CMap.");
+            return;
+        }
         this.cidMappings.addAll(another.cidMappings);
         this.codeSpaces.addAll(another.codeSpaces);
         this.notDefMappings.addAll(another.notDefMappings);