src/jdk.jdeps/share/classes/com/sun/tools/javap/BasicWriter.java

@@ -57,10 +57,12 @@
      protected Set<AccessFlag> flagsReportUnknown(AccessFlags flags, ClassFileFormatVersion cffv) {
          return maskToAccessFlagsReportUnknown(flags.flagsMask(), flags.location(), cffv);
      }
  
      protected Set<AccessFlag> maskToAccessFlagsReportUnknown(int mask, AccessFlag.Location location, ClassFileFormatVersion cffv) {
+         if (cffv == null)
+             cffv = ClassFileFormatVersion.CURRENT_PREVIEW_FEATURES; // Aggressive fallback
          try {
              return AccessFlag.maskToAccessFlags(mask, location, cffv);
          } catch (IllegalArgumentException ex) {
              mask &= location.flagsMask(cffv);
              report("Access Flags: " + ex.getMessage());