src/java.base/share/classes/sun/nio/cs/US_ASCII.java

*** 144,153 ****
--- 144,157 ----
                  else
                      dst[dp++] = repl;
              }
              return dp;
          }
+ 
+         public boolean isASCIICompatible() {
+             return true;
+         }
      }
  
      private static class Encoder extends CharsetEncoder
                                   implements ArrayEncoder {
  
*** 257,264 ****
--- 261,272 ----
                  }
                  dst[dp++] = repl;
              }
              return dp;
          }
+ 
+         public boolean isASCIICompatible() {
+             return true;
+         }
      }
  
  }