Communication between APEX code and WebService hosted in IIS

We have WebService hosted on IIS.

We have configured inbound SSL connection to the site by self-signed certificate. This certificate is not trusted on usual PC because we are using its in for debug purposes.

We trying to call our web service from APEX code by execute SOAP stub.

We have the following error: IO Exception: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

As I understand this error means that salesforce APEX virtual machine does not trust our self-signed certificate, is not it?

How to avoid this?

Communication between APEX code and WebService hosted in IIS

We have WebService hosted on IIS.

We have configured inbound SSL connection to the site by self-signed certificate. This certificate is not trusted on usual PC because we are using its in for debug purposes.

We trying to call our web service from APEX code by execute SOAP stub.

We have the following error: IO Exception: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

As I understand this error means that salesforce APEX virtual machine does not trust our self-signed certificate, is not it?

How to avoid this?