src/jdk.jlink/share/classes/jdk/tools/jlink/internal/plugins/SystemModulesPlugin.java

*** 769,779 ****
                  mv.visitVarInsn(ALOAD, BUILDER_VAR);
  
                  if (md.isOpen()) {
                      setModuleBit("open", true);
                  }
!                 if (md.isSynthetic()) {
                      setModuleBit("synthetic", true);
                  }
              }
  
              /*
--- 769,779 ----
                  mv.visitVarInsn(ALOAD, BUILDER_VAR);
  
                  if (md.isOpen()) {
                      setModuleBit("open", true);
                  }
!                 if (md.modifiers().contains(ModuleDescriptor.Modifier.SYNTHETIC)) {
                      setModuleBit("synthetic", true);
                  }
              }
  
              /*