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Over-the-air reprogramming is an important aspect in the deployment and management of Wireless Sensor Networks (WSNs). However, WSNs reprogramming poses significant challenges due to scarce available energy, low computational power, and limited memory capabilities of the WSNs nodes; all are required for transmission and processing of the created patches. In existing reprogramming schemes, any change in the program layout and/or global variables, produces a significantly large patch size, hence consumes the node's limited resources. Furthermore, to apply the patch, existing schemes require rewriting internal flash, large volume of external flash, as well as rebooting the node. In this paper, we devise a novel reprogramming scheme that we call Queen's Differential (QDiff), which mitigates the effects of program layout changes and retains the maximum similarity between ”old” and ”new” codes using clone detection techniques. Moreover, QDiff organizes the global variables in a novel way to eliminate the effect of variable shifting. To assess the performance of Qdiff, we have carried out a TinyOS implementation using an IRIS mote platform. Our experiments show that QDiff requires near-zero external flash, and significantly lower internal flash rewriting and transmission overhead than leading existing differential reprogramming mechanisms.