I am using drools 5.3.0 and work in osgi environment. i have installed drools-core, drools-api, drools-compiler and drools-tempalte in osgi context. I have no problem to load knowledgebase but get error when fire rules, please see below error message. Does anyone know how to fix it? java.lang.LinkageError: loader constraint violation: when resolving interface method "org.drools.spi.KnowledgeHelper.update(Lorg/drools/FactHandle;)V" the class loader (instance of org/drools/rule/JavaDialectRuntimeData$PackageClassLoader) of the current class, defaultpkg/Rule_ScanRange__startLocationCheck, and the class loader (instance of org/eclipse/osgi/internal/baseadaptor/DefaultClassLoader) for resolved class, org/drools/spi/KnowledgeHelper, have different Class objects for the type org/drools/FactHandle used in the signature java.lang.LinkageError: loader constraint violation: when resolving interface method "org.drools.spi.KnowledgeHelper.update(Lorg/drools/FactHandle;)V" the class loader (instance of org/drools/rule/JavaDialectRuntimeData$PackageClassLoader) of the current class, defaultpkg/Rule_ScanRange__startLocationCheck, and the class loader (instance of org/eclipse/osgi/internal/baseadaptor/DefaultClassLoader) for resolved class, org/drools/spi/KnowledgeHelper, have different Class objects for the type org/drools/FactHandle used in the signature -- View this message in context: http://drools.46999.n3.nabble.com/drools5-3-0-rule-time-error-with-osgi-e... Sent from the Drools: User forum mailing list archive at Nabble.com.