Java reflection to set static final field fails after previous reflection

In Java, it turns out that field accessors get cached, and using accessors has side-effects. For example:

class A {
    private static final int FOO = 5;
}

Field f = A.class.getDeclaredField("FOO");
f.setAccessible(true);
f.getInt(null); // succeeds

Field mf = Field.class.getDeclaredField("modifiers" );
mf.setAccessible(true);

f = A.class.getDeclaredField("FOO");
f.setAccessible(true);
mf.setInt(f, f.getModifiers() & ~Modifier.FINAL);
f.setInt(null, 6); // fails

whereas

class A {
    private static final int FOO = 5;
}

Field mf = Field.class.getDeclaredField("modifiers" );
mf.setAccessible(true);

f = A.class.getDeclaredField("FOO");
f.setAccessible(true);
mf.setInt(f, f.getModifiers() & ~Modifier.FINAL);
f.setInt(null, 6); // succeeds

Here's the relevant bit of the stack trace for the failure:

java.lang.IllegalAccessException: Can not set static final int field A.FOO to (int)6
    at sun.reflect.UnsafeFieldAccessorImpl.throwFinalFieldIllegalAccessException(UnsafeFieldAccessorImpl.java:76)
    at sun.reflect.UnsafeFieldAccessorImpl.throwFinalFieldIllegalAccessException(UnsafeFieldAccessorImpl.java:100)
    at sun.reflect.UnsafeQualifiedStaticIntegerFieldAccessorImpl.setInt(UnsafeQualifiedStaticIntegerFieldAccessorImpl.java:129)
    at java.lang.reflect.Field.setInt(Field.java:949)

These two reflective accesses are of course happening in very different parts of my code base, and I don't really want to change the first to fix the second. Is there any way to change the second reflective access to ensure it succeeds in both cases?

I tried looking at the Field object, and it doesn't have any methods that seem like they would help. In the debugger, I noticed overrideFieldAccessor is set on the second Field returned in the first example and doesn't see the changes to the modifiers. I'm not sure what to do about it, though.

If it makes a difference, I'm using openjdk-8.