diff --git a/main/src/com/google/refine/expr/functions/arrays/Uniques.java b/main/src/com/google/refine/expr/functions/arrays/Uniques.java
index ed78bd370..f5414c485 100644
--- a/main/src/com/google/refine/expr/functions/arrays/Uniques.java
+++ b/main/src/com/google/refine/expr/functions/arrays/Uniques.java
@@ -33,7 +33,8 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 package com.google.refine.expr.functions.arrays;
 
-import java.util.HashSet;
+import java.util.Arrays;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Properties;
 import java.util.Set;
@@ -51,25 +52,18 @@ public class Uniques implements Function {
     public Object call(Properties bindings, Object[] args) {
         if (args.length == 1) {
             Object v = args[0];
-            
+
             if (v != null) {
                 if (v instanceof ArrayNode) {
                     v = JSONUtilities.toArray((ArrayNode) v);
                 }
-                
-                if (v.getClass().isArray() || v instanceof List<?>) {
-                    Set<Object> set = null;
-                    
-                    if (v.getClass().isArray()) {
-                        Object[] a = (Object[]) v;
-                        
-                        set = new HashSet<Object>(a.length);
-                        for (Object element : a) {
-                            set.add(element);
-                        }
-                    } else {
-                        set = new HashSet<Object>(ExpressionUtils.toObjectList(v));
-                    }
+                Set<Object> set = null;
+                if (v.getClass().isArray()) {
+                    set = new LinkedHashSet<Object>(Arrays.asList((Object[]) v));
+                } else if (v instanceof List<?>) {
+                    set = new LinkedHashSet<Object>(ExpressionUtils.toObjectList(v));
+                }
+                if (set != null) {
                     return set.toArray();
                 }
             }
diff --git a/main/tests/server/src/com/google/refine/expr/functions/arrays/UniquesTests.java b/main/tests/server/src/com/google/refine/expr/functions/arrays/UniquesTests.java
index ca85c6e37..e592ece17 100644
--- a/main/tests/server/src/com/google/refine/expr/functions/arrays/UniquesTests.java
+++ b/main/tests/server/src/com/google/refine/expr/functions/arrays/UniquesTests.java
@@ -28,13 +28,47 @@ package com.google.refine.expr.functions.arrays;
 
 import org.testng.annotations.Test;
 
+import com.google.refine.RefineTest;
+import com.google.refine.expr.ParsingException;
 import com.google.refine.util.TestUtils;
 
-public class UniquesTests {
+public class UniquesTests extends RefineTest {
     @Test
     public void serializeUniques() {
         String json = "{\"description\":\"Returns array a with duplicates removed\",\"params\":\"array a\",\"returns\":\"array\"}";
         TestUtils.isSerializedTo(new Uniques(), json);
     }
+
+    public void uniquesJsonArray() throws ParsingException {
+        String[] test = {"'[2,1,1,3]'.parseJson().uniques().toString()", "[2, 1, 3]"};
+        parseEval(bindings, test);
+        String[] test1 = {"'[2,2,null,null,3,3]'.parseJson().uniques().toString()", "[2, null, 3]"};
+        parseEval(bindings, test1);
+    }
+
+    @Test
+    public void uniquesArray() throws ParsingException {
+        String[] test = {"[2,1,1,3].uniques().toString()", "[2, 1, 3]"};
+        parseEval(bindings, test);
+        String[] test1 = {"[2,2,null,null,3,3,3].uniques().toString()", "[2, null, 3]"};
+        parseEval(bindings, test1);
+
+        String[] test2 = {"['z','b','c','c','a'].uniques().toString()", "[z, b, c, a]"};
+        parseEval(bindings, test2);
+        String[] test3 = {"['z','z',null,'c','a'].uniques().toString()", "[z, null, c, a]"};
+        parseEval(bindings, test3);
+
+        String[] test4 = {"[toDate(2020), '2018-03-02'.toDate(), toDate(2020)].uniques().toString()", "[2020-01-01T00:00Z, 2018-03-02T00:00Z]"};
+        parseEval(bindings, test4);
+    }
+
+    @Test
+    public void uniquesMixedArray() throws ParsingException {
+        String[] test = {"[2,1.0,3,1.0].uniques().toString()", "[2, 1.0, 3]"};
+        parseEval(bindings, test);
+        String[] test1 = {"[2,'a',3,3,'a'].uniques().toString()", "[2, a, 3]"};
+        parseEval(bindings, test1);
+    }
+
 }