diff --git a/xl-v1-multipart.go b/xl-v1-multipart.go
index b5fbe11c3..e4539aec9 100644
--- a/xl-v1-multipart.go
+++ b/xl-v1-multipart.go
@@ -444,28 +444,13 @@ func (xl xlObjects) PutObjectPart(bucket, object, uploadID string, partID int, s
 		updatedEInfos = append(updatedEInfos, partsMetadata[index].Erasure)
 	}
 
-	var checksums []checkSumInfo
 	for index, eInfo := range newEInfos {
 		if eInfo.IsValid() {
 			// Use a map to find union of checksums of parts that
 			// we concurrently written and committed before this
 			// part. N B For a different, concurrent upload of the
 			// same part, the last written content remains.
-			checksumSet := make(map[string]checkSumInfo)
-			checksums = newEInfos[index].Checksum
-			for _, cksum := range checksums {
-				checksumSet[cksum.Name] = cksum
-			}
-			checksums = updatedEInfos[index].Checksum
-			for _, cksum := range checksums {
-				checksumSet[cksum.Name] = cksum
-			}
-			// Form the checksumInfo to be committed in xl.json
-			// from the map.
-			var finalChecksums []checkSumInfo
-			for _, cksum := range checksumSet {
-				finalChecksums = append(finalChecksums, cksum)
-			}
+			finalChecksums := unionChecksumInfos(newEInfos[index].Checksum, updatedEInfos[index].Checksum, partSuffix)
 			updatedEInfos[index] = eInfo
 			updatedEInfos[index].Checksum = finalChecksums
 		}
diff --git a/xl-v1-utils.go b/xl-v1-utils.go
index 2f4d73d6e..636e97ff1 100644
--- a/xl-v1-utils.go
+++ b/xl-v1-utils.go
@@ -132,3 +132,41 @@ func readXLMeta(disk StorageAPI, bucket string, object string) (xlMeta xlMetaV1,
 	// Return structured `xl.json`.
 	return xlMeta, nil
 }
+
+// Uses a map to find union of checksums of parts that were concurrently written
+// but committed before this part. N B For a different, concurrent upload of
+// the same part, the ongoing request's data/metadata prevails.
+// cur     - corresponds to parts written to disk before the ongoing putObjectPart request
+// updated - corresponds to parts written to disk while the ongoing putObjectPart is in progress
+// curPartName - name of the part that is being written
+// returns []checkSumInfo containing the set union of checksums of parts that
+// have been written so far incl. the part being written.
+func unionChecksumInfos(cur []checkSumInfo, updated []checkSumInfo, curPartName string) []checkSumInfo {
+	checksumSet := make(map[string]checkSumInfo)
+	var checksums []checkSumInfo
+
+	checksums = cur
+	for _, cksum := range checksums {
+		checksumSet[cksum.Name] = cksum
+	}
+
+	checksums = updated
+	for _, cksum := range checksums {
+		// skip updating checksum of the part that is
+		// written in this request because the checksum
+		// from cur, corresponding to this part,
+		// should remain.
+		if cksum.Name == curPartName {
+			continue
+		}
+		checksumSet[cksum.Name] = cksum
+	}
+
+	// Form the checksumInfo to be committed in xl.json
+	// from the map.
+	var finalChecksums []checkSumInfo
+	for _, cksum := range checksumSet {
+		finalChecksums = append(finalChecksums, cksum)
+	}
+	return finalChecksums
+}
diff --git a/xl-v1-utils_test.go b/xl-v1-utils_test.go
index 03a4378d2..7745c5eb5 100644
--- a/xl-v1-utils_test.go
+++ b/xl-v1-utils_test.go
@@ -41,3 +41,49 @@ func TestReduceErrs(t *testing.T) {
 		}
 	}
 }
+
+// Test for unionChecksums
+func TestUnionChecksumInfos(t *testing.T) {
+	cur := []checkSumInfo{
+		{"part.1", "dummy", "cur-hash.1"},
+		{"part.2", "dummy", "cur-hash.2"},
+		{"part.3", "dummy", "cur-hash.3"},
+		{"part.4", "dummy", "cur-hash.4"},
+		{"part.5", "dummy", "cur-hash.5"},
+	}
+	updated := []checkSumInfo{
+		{"part.1", "dummy", "updated-hash.1"},
+		{"part.2", "dummy", "updated-hash.2"},
+		{"part.3", "dummy", "updated-hash.3"},
+	}
+	curPartcksum := cur[0] // part.1 is the current part being written
+
+	// Verify that hash of current part being written must be from cur []checkSumInfo
+	finalChecksums := unionChecksumInfos(cur, updated, curPartcksum.Name)
+	for _, cksum := range finalChecksums {
+		if cksum.Name == curPartcksum.Name && cksum.Hash != curPartcksum.Hash {
+			t.Errorf("expected Hash = %s but received Hash = %s\n", curPartcksum.Hash, cksum.Hash)
+		}
+	}
+
+	// Verify that all part checksums are present in the union and nothing more.
+	// Map to store all unique part names
+	allPartNames := make(map[string]struct{})
+	// Insert part names from cur and updated []checkSumInfo
+	for _, cksum := range cur {
+		allPartNames[cksum.Name] = struct{}{}
+	}
+	for _, cksum := range updated {
+		allPartNames[cksum.Name] = struct{}{}
+	}
+	// All parts must have an entry in the []checkSumInfo returned from unionChecksums
+	for _, finalcksum := range finalChecksums {
+		if _, ok := allPartNames[finalcksum.Name]; !ok {
+			t.Errorf("expected to find %s but not present in the union, where current part is %s\n",
+				finalcksum.Name, curPartcksum.Name)
+		}
+	}
+	if len(finalChecksums) != len(allPartNames) {
+		t.Error("Union of Checksums doesn't have same number of elements as unique parts in total")
+	}
+}