diff --git a/programs/fileio.c b/programs/fileio.c
index 14569bb4..5e3928ef 100644
--- a/programs/fileio.c
+++ b/programs/fileio.c
@@ -466,6 +466,13 @@ static cRess_t FIO_createCResources(const char* dictFileName, int cLevel,
 #ifdef ZSTD_MULTITHREAD
         DISPLAYLEVEL(5,"set nb workers = %u \n", g_nbWorkers);
         CHECK( ZSTD_CCtx_setParameter(ress.cctx, ZSTD_p_nbWorkers, g_nbWorkers) );
+        if ( (g_overlapLog == FIO_OVERLAP_LOG_NOTSET)
+          && (cLevel == ZSTD_maxCLevel()) )
+            g_overlapLog = 9;   /* full overlap */
+        if (g_overlapLog != FIO_OVERLAP_LOG_NOTSET) {
+            DISPLAYLEVEL(3,"set overlapLog = %u \n", g_overlapLog);
+            CHECK( ZSTD_CCtx_setParameter(ress.cctx, ZSTD_p_overlapSizeLog, g_overlapLog) );
+        }
 #endif
         /* dictionary */
         CHECK( ZSTD_CCtx_setPledgedSrcSize(ress.cctx, srcSize) );  /* set the value temporarily for dictionary loading, to adapt compression parameters */
diff --git a/tests/playTests.sh b/tests/playTests.sh
index 41d8263b..49448022 100755
--- a/tests/playTests.sh
+++ b/tests/playTests.sh
@@ -650,6 +650,25 @@ then
 
     $ECHO "\n===>  zstdmt long distance matching round-trip tests "
     roundTripTest -g8M "3 --long=24 -T2"
+
+    $ECHO "\n===>  ovLog tests "
+    ./datagen -g2MB > tmp
+    refSize=$($ZSTD tmp -6 -c --zstd=wlog=18         | wc -c)
+    ov9Size=$($ZSTD tmp -6 -c --zstd=wlog=18,ovlog=9 | wc -c)
+    ov0Size=$($ZSTD tmp -6 -c --zstd=wlog=18,ovlog=0 | wc -c)
+    if [ $refSize -eq $ov9Size ]; then
+        echo ov9Size should be different from refSize
+        exit 1
+    fi
+    if [ $refSize -eq $ov0Size ]; then
+        echo ov0Size should be different from refSize
+        exit 1
+    fi
+    if [ $ov9Size -ge $ov0Size ]; then
+        echo ov9Size=$ov9Size should be smaller than ov0Size=$ov0Size
+        exit 1
+    fi
+
 else
     $ECHO "\n===>  no multithreading, skipping zstdmt tests "
 fi