The OSGi framework is a Java-based, centralized, component oriented platform. It is being widely adopted as an execution environment for the development of extensible applications. However, current Java Virtual Machines are unable to isolate components from each other. For instance, a malicious component can freeze the complete platform by allocating too much memory or alter the behavior of other components by modifying shared variables. This paper presents I-JVM, a Java Virtual Machine that provides a lightweight approach to isolation while preserving compatibility with legacy OSGi applications. Our evaluation of I-JVM shows that it solves the 8 known OSGi vulnerabilities that are due to the Java Virtual Machine and that the overhead of I-JVM compared to the JVM on which it is based is below 20%.