diff --git a/src/classes/io/simonis/cl4cds.java b/src/classes/io/simonis/cl4cds.java
index ea3c474..dd9b61a 100644
--- a/src/classes/io/simonis/cl4cds.java
+++ b/src/classes/io/simonis/cl4cds.java
@@ -127,7 +127,7 @@ public class cl4cds {
       String line;
       long objectID = 0;
       Set<String> klassSet = new HashSet<>();
-      Map<String, String> nameSourceMap = new HashMap<>();
+      Set<String> klassNameSet = new HashSet<>();
       while((line = in.readLine()) != null) {
         if (firstLine.reset(line).matches()) {
           MatchResult mr1 = firstLine.toMatchResult();
@@ -171,11 +171,12 @@ public class cl4cds {
 
             if ("NULL class loader".equals(loader) ||
                 loader.contains("of <bootloader>") || // this is JDK 11 syntax
+                loader.contains("of 'bootstrap'") || // this is JDK 12 syntax
                 loader.contains("jdk/internal/loader/ClassLoaders$PlatformClassLoader" /* && source == jrt image */) ||
                 loader.contains("jdk/internal/loader/ClassLoaders$AppClassLoader" /* && source == jar file */)) {
               out.println(name.replace('.', '/') + " id: " + klass);
               klassSet.add(klass);
-              nameSourceMap.put(name, source);
+              klassNameSet.add(name);
             }
             else {
               // Custom class loader (currently only supported if classes are loaded from jar files ?)
@@ -216,23 +217,23 @@ public class cl4cds {
                 }
                 continue;
               }
+              if (klassNameSet.contains(name)) {
+                System.err.println("Skipping " + name + " from " + sourceFile + " - reason: already dumped");
+                continue;
+              }
               List<String> deps = new LinkedList<>();
               deps.add(parent);
               if (interf != null) {
                 deps.addAll(Arrays.asList(interf.split("\\s")));
               }
               if (klassSet.containsAll(deps)) {
-                if (source.equals(nameSourceMap.get(name))) {
-                  System.err.println("Skipping " + name + " from " + sourceFile + " - reason: already dumped");
-                  continue;
-                }
                 out.print(name.replace('.', '/') + " id: " + klass + " super: " + parent);
                 if (interf != null) {
                   out.print(" interfaces: " + interf);
                 }
                 out.println(" source: " + sourceFile);
                 klassSet.add(klass);
-                nameSourceMap.put(name, source);
+                klassNameSet.add(name);
               }
               else {
                 System.err.println("Skipping " + name + " from " + sourceFile + " - reason: failed dependencies");