// an important problem for ListBuckets() getting signed with
	// different regions.
	if region == "" {
		region = sRegion
	}
	// Should validate region, only if region is set.
	if !isValidRegion(sRegion, region) {
		return ch, ErrAuthorizationHeaderMalformed
	}
	if credElements[2] != string(stype) {
		if stype == serviceSTS {
			return ch, ErrInvalidServiceSTS
		}
		return ch, ErrInvalidServiceS3

		{"us-west-1", "US", false},
		{"us-west-1", "us-west-1", true},
		// "US" was old naming convention for 'us-east-1'.
		{"US", "US", true},
	}

	for i, testCase := range testCases {
		actualResult := isValidRegion(testCase.inputReqRegion, testCase.inputConfRegion)
		if testCase.expectedResult != actualResult {
			t.Errorf("Test %d: Expected the result to `%v`, but instead got `%v`", i+1, testCase.expectedResult, actualResult)
		}
	}