diff --git a/docs/content/querying/dimensionspecs.md b/docs/content/querying/dimensionspecs.md
index cef946daaab..471d7d84177 100644
--- a/docs/content/querying/dimensionspecs.md
+++ b/docs/content/querying/dimensionspecs.md
@@ -229,9 +229,9 @@ For a regular dimension, it assumes the string is formatted in
 ```json
 { "type" : "timeFormat",
   "format" : <output_format> (optional),
-  "timeZone" : <time_zone> (optional),
-  "locale" : <locale> (optional),
-  "granularity" : <granularity> (optional) },
+  "timeZone" : <time_zone> (optional, default UTC),
+  "locale" : <locale> (optional, default current locale),
+  "granularity" : <granularity> (optional, default none) },
   "asMillis" : <true or false> (optional) }
 ```
 
diff --git a/processing/src/main/java/io/druid/query/extraction/TimeFormatExtractionFn.java b/processing/src/main/java/io/druid/query/extraction/TimeFormatExtractionFn.java
index 16c18126db1..6e096b67e72 100644
--- a/processing/src/main/java/io/druid/query/extraction/TimeFormatExtractionFn.java
+++ b/processing/src/main/java/io/druid/query/extraction/TimeFormatExtractionFn.java
@@ -106,7 +106,9 @@ public class TimeFormatExtractionFn implements ExtractionFn
   @Override
   public byte[] getCacheKey()
   {
-    final byte[] exprBytes = StringUtils.toUtf8(format + "\u0001" + tz.getID() + "\u0001" + locale.toLanguageTag());
+    final String tzId = (tz == null ? DateTimeZone.UTC : tz).getID();
+    final String localeTag = (locale == null ? Locale.getDefault() : locale).toLanguageTag();
+    final byte[] exprBytes = StringUtils.toUtf8(format + "\u0001" + tzId + "\u0001" + localeTag);
     final byte[] granularityCacheKey = granularity.getCacheKey();
     return ByteBuffer.allocate(4 + exprBytes.length + granularityCacheKey.length)
                      .put(ExtractionCacheHelper.CACHE_TYPE_ID_TIME_FORMAT)
diff --git a/processing/src/test/java/io/druid/query/extraction/TimeFormatExtractionFnTest.java b/processing/src/test/java/io/druid/query/extraction/TimeFormatExtractionFnTest.java
index 37a8b2529a0..0ed454071e1 100644
--- a/processing/src/test/java/io/druid/query/extraction/TimeFormatExtractionFnTest.java
+++ b/processing/src/test/java/io/druid/query/extraction/TimeFormatExtractionFnTest.java
@@ -171,7 +171,16 @@ public class TimeFormatExtractionFnTest
         true
     );
 
+    TimeFormatExtractionFn fn4 = new TimeFormatExtractionFn(
+        null,
+        null,
+        null,
+        null,
+        false
+    );
+
     Assert.assertFalse(Arrays.equals(fn.getCacheKey(), fn2.getCacheKey()));
+    Assert.assertFalse(Arrays.equals(fn.getCacheKey(), fn4.getCacheKey()));
     Assert.assertTrue(Arrays.equals(fn2.getCacheKey(), fn3.getCacheKey()));
   }
 }