diff --git a/cmd/auth-handler.go b/cmd/auth-handler.go
index a4578af5b..9a163cc52 100644
--- a/cmd/auth-handler.go
+++ b/cmd/auth-handler.go
@@ -272,7 +272,7 @@ func checkRequestAuthTypeToAccessKey(ctx context.Context, r *http.Request, actio
 	var cred auth.Credentials
 	switch getRequestAuthType(r) {
 	case authTypeUnknown, authTypeStreamingSigned:
-		return accessKey, owner, ErrAccessDenied
+		return accessKey, owner, ErrSignatureVersionNotSupported
 	case authTypePresignedV2, authTypeSignedV2:
 		if s3Err = isReqAuthenticatedV2(r); s3Err != ErrNone {
 			return accessKey, owner, s3Err
@@ -334,7 +334,7 @@ func checkRequestAuthTypeToAccessKey(ctx context.Context, r *http.Request, actio
 			// Request is allowed return the appropriate access key.
 			return cred.AccessKey, owner, ErrNone
 		}
-		return accessKey, owner, ErrAccessDenied
+		return cred.AccessKey, owner, ErrAccessDenied
 	}
 	if globalIAMSys.IsAllowed(iampolicy.Args{
 		AccountName:     cred.AccessKey,
@@ -348,7 +348,7 @@ func checkRequestAuthTypeToAccessKey(ctx context.Context, r *http.Request, actio
 		// Request is allowed return the appropriate access key.
 		return cred.AccessKey, owner, ErrNone
 	}
-	return accessKey, owner, ErrAccessDenied
+	return cred.AccessKey, owner, ErrAccessDenied
 }
 
 // Verify if request has valid AWS Signature Version '2'.
@@ -472,7 +472,7 @@ func isPutActionAllowed(atype authType, bucketName, objectName string, r *http.R
 	var owner bool
 	switch atype {
 	case authTypeUnknown:
-		return ErrAccessDenied
+		return ErrSignatureVersionNotSupported
 	case authTypeSignedV2, authTypePresignedV2:
 		cred, owner, s3Err = getReqAccessKeyV2(r)
 	case authTypeStreamingSigned, authTypePresigned, authTypeSigned:
diff --git a/cmd/bucket-handlers.go b/cmd/bucket-handlers.go
index 33917edd2..17865a4c2 100644
--- a/cmd/bucket-handlers.go
+++ b/cmd/bucket-handlers.go
@@ -266,7 +266,7 @@ func (api objectAPIHandlers) ListBucketsHandler(w http.ResponseWriter, r *http.R
 	listBuckets := objectAPI.ListBuckets
 
 	accessKey, owner, s3Error := checkRequestAuthTypeToAccessKey(ctx, r, policy.ListAllMyBucketsAction, "", "")
-	if s3Error != ErrNone {
+	if s3Error != ErrNone && s3Error != ErrAccessDenied {
 		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(s3Error), r.URL, guessIsBrowserReq(r))
 		return
 	}
@@ -295,32 +295,43 @@ func (api objectAPIHandlers) ListBucketsHandler(w http.ResponseWriter, r *http.R
 		}
 	}
 
-	// Set prefix value for "s3:prefix" policy conditionals.
-	r.Header.Set("prefix", "")
-
-	// Set delimiter value for "s3:delimiter" policy conditionals.
-	r.Header.Set("delimiter", SlashSeparator)
-
-	// err will be nil here as we already called this function
-	// earlier in this request.
-	claims, _ := getClaimsFromToken(r)
-	var newBucketsInfo []BucketInfo
-	for _, bucketInfo := range bucketsInfo {
-		if globalIAMSys.IsAllowed(iampolicy.Args{
-			AccountName:     accessKey,
-			Action:          iampolicy.ListBucketAction,
-			BucketName:      bucketInfo.Name,
-			ConditionValues: getConditionValues(r, "", accessKey, claims),
-			IsOwner:         owner,
-			ObjectName:      "",
-			Claims:          claims,
-		}) {
-			newBucketsInfo = append(newBucketsInfo, bucketInfo)
+	if s3Error == ErrAccessDenied {
+		// Set prefix value for "s3:prefix" policy conditionals.
+		r.Header.Set("prefix", "")
+
+		// Set delimiter value for "s3:delimiter" policy conditionals.
+		r.Header.Set("delimiter", SlashSeparator)
+
+		// err will be nil here as we already called this function
+		// earlier in this request.
+		claims, _ := getClaimsFromToken(r)
+		n := 0
+		// Use the following trick to filter in place
+		// https://github.com/golang/go/wiki/SliceTricks#filter-in-place
+		for _, bucketInfo := range bucketsInfo {
+			if globalIAMSys.IsAllowed(iampolicy.Args{
+				AccountName:     accessKey,
+				Action:          iampolicy.ListBucketAction,
+				BucketName:      bucketInfo.Name,
+				ConditionValues: getConditionValues(r, "", accessKey, claims),
+				IsOwner:         owner,
+				ObjectName:      "",
+				Claims:          claims,
+			}) {
+				bucketsInfo[n] = bucketInfo
+				n++
+			}
+		}
+		bucketsInfo = bucketsInfo[:n]
+		// No buckets can be filtered return access denied error.
+		if len(bucketsInfo) == 0 {
+			writeErrorResponse(ctx, w, errorCodes.ToAPIErr(s3Error), r.URL, guessIsBrowserReq(r))
+			return
 		}
 	}
 
 	// Generate response.
-	response := generateListBucketsResponse(newBucketsInfo)
+	response := generateListBucketsResponse(bucketsInfo)
 	encodedSuccessResponse := encodeResponse(response)
 
 	// Write response.
diff --git a/cmd/test-utils_test.go b/cmd/test-utils_test.go
index 6200540f4..6813dc37d 100644
--- a/cmd/test-utils_test.go
+++ b/cmd/test-utils_test.go
@@ -1737,9 +1737,9 @@ func ExecObjectLayerAPIAnonTest(t *testing.T, obj ObjectLayer, testName, bucketN
 	apiRouter.ServeHTTP(rec, anonReq)
 
 	// expected error response when the unsigned HTTP request is not permitted.
-	accesDeniedHTTPStatus := getAPIError(ErrAccessDenied).HTTPStatusCode
-	if rec.Code != accesDeniedHTTPStatus {
-		t.Fatal(failTestStr(anonTestStr, fmt.Sprintf("Object API Nil Test expected to fail with %d, but failed with %d", accesDeniedHTTPStatus, rec.Code)))
+	accessDenied := getAPIError(ErrAccessDenied).HTTPStatusCode
+	if rec.Code != accessDenied {
+		t.Fatal(failTestStr(anonTestStr, fmt.Sprintf("Object API Nil Test expected to fail with %d, but failed with %d", accessDenied, rec.Code)))
 	}
 
 	// HEAD HTTTP request doesn't contain response body.
@@ -1826,8 +1826,10 @@ func ExecObjectLayerAPIAnonTest(t *testing.T, obj ObjectLayer, testName, bucketN
 		}
 	}
 
-	if rec.Code != accesDeniedHTTPStatus {
-		t.Fatal(failTestStr(unknownSignTestStr, fmt.Sprintf("Object API Unknow auth test for \"%s\", expected to fail with %d, but failed with %d", testName, accesDeniedHTTPStatus, rec.Code)))
+	// expected error response when the unsigned HTTP request is not permitted.
+	unsupportedSignature := getAPIError(ErrSignatureVersionNotSupported).HTTPStatusCode
+	if rec.Code != unsupportedSignature {
+		t.Fatal(failTestStr(unknownSignTestStr, fmt.Sprintf("Object API Unknow auth test for \"%s\", expected to fail with %d, but failed with %d", testName, unsupportedSignature, rec.Code)))
 	}
 
 }