diff --git a/lib/dictBuilder/cover.c b/lib/dictBuilder/cover.c
index 621996759..4721205da 100644
--- a/lib/dictBuilder/cover.c
+++ b/lib/dictBuilder/cover.c
@@ -919,13 +919,12 @@ void COVER_best_finish(COVER_best_t *best, ZDICT_cover_params_t parameters,
         }
       }
       /* Save the dictionary, parameters, and size */
-      if (!dict) {
-        return;
+      if (dict) {
+        memcpy(best->dict, dict, dictSize);
+        best->dictSize = dictSize;
+        best->parameters = parameters;
+        best->compressedSize = compressedSize;
       }
-      memcpy(best->dict, dict, dictSize);
-      best->dictSize = dictSize;
-      best->parameters = parameters;
-      best->compressedSize = compressedSize;
     }
     if (liveJobs == 0) {
       ZSTD_pthread_cond_broadcast(&best->cond);
diff --git a/tests/playTests.sh b/tests/playTests.sh
index ad096fddd..19fc514f6 100755
--- a/tests/playTests.sh
+++ b/tests/playTests.sh
@@ -526,6 +526,15 @@ $ZSTD -o tmpDict --train "$TESTDIR"/*.c "$PRGDIR"/*.c
 test -f tmpDict
 $ZSTD --train "$TESTDIR"/*.c "$PRGDIR"/*.c
 test -f dictionary
+println "- Test dictionary training fails"
+echo "000000000000000000000000000000000" > tmpz
+$ZSTD --train tmpz tmpz tmpz tmpz tmpz tmpz tmpz tmpz tmpz && die "Dictionary training should fail : source is all zeros"
+if [ -n "$hasMT" ]
+then
+  $ZSTD --train -T0 tmpz tmpz tmpz tmpz tmpz tmpz tmpz tmpz tmpz && die "Dictionary training should fail : source is all zeros"
+  println "- Create dictionary with multithreading enabled"
+  $ZSTD --train -T0 "$TESTDIR"/*.c "$PRGDIR"/*.c -o tmpDict
+fi
 rm tmp* dictionary