diff --git a/.travis.yml b/.travis.yml
index e17dba64..ec1adab0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -34,7 +34,8 @@ matrix:
 
     - name: make test (complete)
       script:
-        - make test
+        # DEVNULLRIGHTS : will request sudo rights to test permissions on /dev/null
+        - DEVNULLRIGHTS=test make test
 
     - name: gcc-6 + gcc-7 compilation
       script:
diff --git a/programs/fileio.c b/programs/fileio.c
index 98337672..60b70453 100644
--- a/programs/fileio.c
+++ b/programs/fileio.c
@@ -609,7 +609,10 @@ FIO_openDstFile(FIO_prefs_t* const prefs,
     {   FILE* const f = fopen( dstFileName, "wb" );
         if (f == NULL) {
             DISPLAYLEVEL(1, "zstd: %s: %s\n", dstFileName, strerror(errno));
-        } else if(srcFileName != NULL && strcmp (srcFileName, stdinmark)) {
+        } else if (srcFileName != NULL
+               && strcmp (srcFileName, stdinmark)
+               && strcmp(dstFileName, nulmark) ) {
+            /* reduce rights on newly created dst file while compression is ongoing */
             chmod(dstFileName, 00600);
         }
         return f;
@@ -1393,7 +1396,7 @@ static int FIO_compressFilename_dstFile(FIO_prefs_t* const prefs,
     assert(ress.srcFile != NULL);
     if (ress.dstFile == NULL) {
         closeDstFile = 1;
-        DISPLAYLEVEL(6, "FIO_compressFilename_dstFile: opening dst: %s", dstFileName);
+        DISPLAYLEVEL(6, "FIO_compressFilename_dstFile: opening dst: %s \n", dstFileName);
         ress.dstFile = FIO_openDstFile(prefs, srcFileName, dstFileName);
         if (ress.dstFile==NULL) return 1;  /* could not open dstFileName */
         /* Must only be added after FIO_openDstFile() succeeds.
@@ -1415,6 +1418,7 @@ static int FIO_compressFilename_dstFile(FIO_prefs_t* const prefs,
 
         clearHandler();
 
+        DISPLAYLEVEL(6, "FIO_compressFilename_dstFile: closing dst: %s \n", dstFileName);
         if (fclose(dstFile)) { /* error closing dstFile */
             DISPLAYLEVEL(1, "zstd: %s: %s \n", dstFileName, strerror(errno));
             result=1;
@@ -1427,7 +1431,10 @@ static int FIO_compressFilename_dstFile(FIO_prefs_t* const prefs,
         } else if ( strcmp(dstFileName, stdoutmark)
                  && strcmp(dstFileName, nulmark)
                  && transfer_permissions) {
+            DISPLAYLEVEL(6, "FIO_compressFilename_dstFile: transfering permissions into dst: %s \n", dstFileName);
             UTIL_setFileStat(dstFileName, &statbuf);
+        } else {
+            DISPLAYLEVEL(6, "FIO_compressFilename_dstFile: do not transfer permissions into dst: %s \n", dstFileName);
         }
     }
 
@@ -1462,6 +1469,7 @@ FIO_compressFilename_srcFile(FIO_prefs_t* const prefs,
                              int compressionLevel)
 {
     int result;
+    DISPLAYLEVEL(6, "FIO_compressFilename_srcFile: %s \n", srcFileName);
 
     /* ensure src is not a directory */
     if (UTIL_isDirectory(srcFileName)) {
diff --git a/tests/playTests.sh b/tests/playTests.sh
index 4bb75d2f..6359076c 100755
--- a/tests/playTests.sh
+++ b/tests/playTests.sh
@@ -220,13 +220,12 @@ $ZSTD tmp -c --compress-literals    -19      | $ZSTD -t
 $ZSTD -b --fast=1 -i0e1 tmp --compress-literals
 $ZSTD -b --fast=1 -i0e1 tmp --no-compress-literals
 
-println "test: --exclude-compressed flag"
+println "\n===>  --exclude-compressed flag"
 rm -rf precompressedFilterTestDir
 mkdir -p precompressedFilterTestDir
 ./datagen $size > precompressedFilterTestDir/input.5
 ./datagen $size > precompressedFilterTestDir/input.6
 $ZSTD --exclude-compressed --long --rm -r precompressedFilterTestDir
-sleep 5
 ./datagen $size > precompressedFilterTestDir/input.7
 ./datagen $size > precompressedFilterTestDir/input.8
 $ZSTD --exclude-compressed --long --rm -r precompressedFilterTestDir
@@ -251,7 +250,7 @@ test -f precompressedFilterTestDir/input.5.zst.zst
 test -f precompressedFilterTestDir/input.6.zst.zst
 println "Test completed"
 
-println "test : file removal"
+println "\n===>  file removal"
 $ZSTD -f --rm tmp
 test ! -f tmp  # tmp should no longer be present
 $ZSTD -f -d --rm tmp.zst
@@ -278,13 +277,16 @@ $ZSTD -f tmp && die "attempt to compress a non existing file"
 test -f tmp.zst  # destination file should still be present
 rm -rf tmp*  # may also erase tmp* directory from previous failed run
 
-println "\n===> decompression only tests "
-dd bs=1 count=1048576 if=/dev/zero of=tmp
+println "\n===>  decompression only tests "
+# the following test verifies that the decoder is compatible with RLE as first block
+# older versions of zstd cli are not able to decode such corner case.
+# As a consequence, the zstd cli do not generate them, to maintain compatibility with older versions.
+dd bs=1048576 count=1 if=/dev/zero of=tmp
 $ZSTD -d -o tmp1 "$TESTDIR/golden-decompression/rle-first-block.zst"
 $DIFF -s tmp1 tmp
 rm tmp*
 
-println "test : compress multiple files"
+println "\m===>  compress multiple files"
 println hello > tmp1
 println world > tmp2
 $ZSTD tmp1 tmp2 -o "$INTOVOID" -f
@@ -306,7 +308,17 @@ if [ "$?" -eq 139 ]; then
 fi
 rm tmp*
 
-println "test : compress multiple files into an output directory, --output-dir-flat"
+if [ -n "$DEVNULLRIGHTS" ]
+then
+    # these tests requires sudo rights, which is uncommon.
+    # they are only triggered if DEVNULLRIGHTS macro is defined.
+    println "\n===> checking /dev/null permissions are unaltered "
+    ./datagen > tmp
+    sudo $ZSTD tmp -o $INTOVOID   # sudo rights could modify /dev/null permissions
+    ls -las $INTOVOID | grep "rw-rw-rw-"
+fi
+
+println "\n===>  compress multiple files into an output directory, --output-dir-flat"
 println henlo > tmp1
 mkdir tmpInputTestDir
 mkdir tmpInputTestDir/we
@@ -352,7 +364,6 @@ $ZSTD -dcf tmp1
 
 
 println "\n===>  frame concatenation "
-
 println "hello " > hello.tmp
 println "world!" > world.tmp
 cat hello.tmp world.tmp > helloworld.tmp