We present PRISM, a novel technique for detecting overfitting patches in automatic program repair (APR). Despite significant advances in APR, overfitting patches—those passing test suites but not fixing bugs—persist, degrading performance and increasing developer review burden. To mitigate overfitting, various automatic patch correctness classification (APCC) techniques have been proposed. However, while accurate, existing APCC methods often mislabel scarce correct patches as incorrect, significantly lowering the APR fix rate. To address this, we propose (1) novel semantic features capturing patch-induced behavioral changes and (2) a tailored learning algorithm that preserves correct patches while filtering incorrect ones. Experiments on ranked patch data from 10 APR tools show that PRISM uniquely reduces review burden and finds more correct patches. Other methods lower the fix rate by misclassifying correct patches. Evaluations on 1,829 labeled patches confirm Prism removes more incorrect patches at equal correct patch preservation rates.