diff --git a/azkaban-common/src/main/java/azkaban/utils/OsMemoryUtil.java b/azkaban-common/src/main/java/azkaban/utils/OsMemoryUtil.java
index 5c46789..f1bc736 100644
--- a/azkaban-common/src/main/java/azkaban/utils/OsMemoryUtil.java
+++ b/azkaban-common/src/main/java/azkaban/utils/OsMemoryUtil.java
@@ -6,7 +6,6 @@ import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;
-import java.util.Set;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
@@ -24,7 +23,7 @@ class OsMemoryUtil {
// This file is used by Linux. It doesn't exist on Mac for example.
private static final String MEM_INFO_FILE = "/proc/meminfo";
- private static final Set<String> MEM_KEYS = ImmutableSet
+ private static final ImmutableSet<String> MEM_KEYS = ImmutableSet
.of("MemFree", "Buffers", "Cached", "SwapFree");
/**
