A DESCRIPTION OF THE PROBLEM :
When debugging the SunPKCS11 configuration for a Yubikey 5, I noticed that setting java.security.debug=sunpkcs11 breaks the configuration if the slotListIndex parameter is used.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the following code, with and without -Djava.security.debug=sunpkcs11

      PKCS11 pkcs11 = PKCS11.getInstance("C:\\Program Files\\Yubico\\Yubico PIV Tool\\bin\\libykcs11.dll", "C_GetFunctionList", null, false);
      long slot = pkcs11.C_GetSlotList(true)[0]; // slot = 2

      String configuration = "--name=yubikey\n" +
              "library = \"C:/Program Files/Yubico/Yubico PIV Tool/bin/libykcs11.dll\"\n" +
              "slotListIndex=" + slot;

      Provider provider = Security.getProvider("SunPKCS11");
      provider.configure(configuration);

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
No exception thrown, the provider is properly initialized.
ACTUAL -
When java.security.debug=sunpkcs11 is set an exception is thrown. Here is the output:

SunPKCS11 loading --name=yubikey
library = "C:/Program Files/Yubico/Yubico PIV Tool/bin/libykcs11.dll"
slotListIndex=2
sunpkcs11: Initializing PKCS#11 library C:/Program Files/Yubico/Yubico PIV Tool/bin/libykcs11.dll
Information for provider SunPKCS11-yubikey
Library info:
  cryptokiVersion: 2.40
  manufacturerID: Yubico (www.yubico.com)
  flags: 0
  libraryDescription: PKCS#11 PIV Library (SP-800-73)
  libraryVersion: 2.30
All slots: 0, 1, 2
Slots with tokens: 2

java.security.ProviderException: Initialization failed
at jdk.crypto.cryptoki/sun.security.pkcs11.SunPKCS11.<init>(SunPKCS11.java:387)
at jdk.crypto.cryptoki/sun.security.pkcs11.SunPKCS11$1.run(SunPKCS11.java:118)
at jdk.crypto.cryptoki/sun.security.pkcs11.SunPKCS11$1.run(SunPKCS11.java:115)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:569)
at jdk.crypto.cryptoki/sun.security.pkcs11.SunPKCS11.configure(SunPKCS11.java:115)
... 32 more
Caused by: java.security.ProviderException: slotListIndex is 2 but token only has 1 slots
at jdk.crypto.cryptoki/sun.security.pkcs11.SunPKCS11.<init>(SunPKCS11.java:368)
... 36 more


---------- BEGIN SOURCE ----------
import java.security.Provider;
import java.security.Security;

import org.junit.Test;
import sun.security.pkcs11.wrapper.PKCS11;

public class SunPKCS11Test {

    @Test
    public void testSunPKCS11() throws Exception {
        PKCS11 pkcs11 = PKCS11.getInstance("C:\\Program Files\\Yubico\\Yubico PIV Tool\\bin\\libykcs11.dll", "C_GetFunctionList", null, false);
        long slot = pkcs11.C_GetSlotList(true)[0]; // slot = 2

        String configuration = "--name=yubikey\n" +
                "library = \"C:/Program Files/Yubico/Yubico PIV Tool/bin/libykcs11.dll\"\n" +
                "slotListIndex=" + slot;

        Provider provider = Security.getProvider("SunPKCS11");
        provider.configure(configuration);
    }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Replace the 'slotListIndex' parameter with 'slot'

FREQUENCY : always