diff --git a/lib/compress/zstd_opt.h b/lib/compress/zstd_opt.h
index 387d62400..9496ed358 100644
--- a/lib/compress/zstd_opt.h
+++ b/lib/compress/zstd_opt.h
@@ -885,7 +885,7 @@ void ZSTD_compressBlock_opt_extDict_generic(ZSTD_CCtx* ctx,
                     const U32 repIndex = (U32)(current+cur - opt[cur].rep[i]);
                     const BYTE* const repBase = repIndex < dictLimit ? dictBase : base;
                     const BYTE* const repMatch = repBase + repIndex;
-                    if ((rep[i]<(U32)(ip-prefixStart))
+                    if ((opt[cur].rep[i]<(U32)(ip-prefixStart))
                       && (((U32)((dictLimit-1) - repIndex) >= 3) & (repIndex>lowestIndex))  /* intentional overflow */
                       && (MEM_readMINMATCH(inr, minMatch) == MEM_readMINMATCH(repMatch, minMatch)) ) {
                         /* repcode detected */