diff --git a/README.md b/README.md
index f6f8fb1..f35c74f 100644
--- a/README.md
+++ b/README.md
@@ -99,17 +99,18 @@ Where
 
 ```ruby
 where: {
-  expires_at: {gt: Time.now}, # lt, gte, lte also available
-  orders_count: 1..10,        # equivalent to {gte: 1, lte: 10}
-  aisle_id: [25, 30],         # in
-  store_id: {not: 2},         # not
-  aisle_id: {not: [25, 30]},  # not in
-  user_ids: {all: [1, 3]},    # all elements in array
-  category: /frozen .+/,      # regexp
-  store_id: {_exists: true},  # exists [master]
+  expires_at: {gt: Time.now},   # lt, gte, lte also available
+  orders_count: 1..10,          # equivalent to {gte: 1, lte: 10}
+  aisle_id: [25, 30],           # in
+  store_id: {not: 2},           # not
+  aisle_id: {not: [25, 30]},    # not in
+  user_ids: {all: [1, 3]},      # all elements in array
+  category: /frozen .+/,        # regexp
+  store_id: {exists: true},     # exists [master]
+  category: {prefix: "Frozen"}, # prefix
   _or: [{in_stock: true}, {backordered: true}],
   _and: [{in_stock: true}, {backordered: true}],
-  _not: {store_id: 1}         # negate a condition
+  _not: {store_id: 1}           # negate a condition
 }
 ```
 
diff --git a/lib/searchkick/query.rb b/lib/searchkick/query.rb
index 621b038..fe5a965 100644
--- a/lib/searchkick/query.rb
+++ b/lib/searchkick/query.rb
@@ -945,7 +945,7 @@ module Searchkick
                 end
               when :in
                 filters << term_filters(field, op_value)
-              when :_exists
+              when :exists
                 filters << {exists: {field: field}}
               else
                 range_query =
diff --git a/test/where_test.rb b/test/where_test.rb
index b40ff96..b1c590b 100644
--- a/test/where_test.rb
+++ b/test/where_test.rb
@@ -68,8 +68,8 @@ class WhereTest < Minitest::Test
     assert_search "product", ["Product B", "Product C"], where: {user_ids: {_not: [2], in: [1, 3]}}
 
     # exists
-    assert_search "product", ["Product A", "Product B", "Product C"], where: {user_ids: {_exists: true}}
-    assert_search "product", ["Product A", "Product B", "Product C", "Product D"], where: {store_id: {_exists: true}}
+    assert_search "product", ["Product A", "Product B", "Product C"], where: {user_ids: {exists: true}}
+    assert_search "product", ["Product A", "Product B", "Product C", "Product D"], where: {store_id: {exists: true}}
 
     # not
     assert_search "product", ["Product D"], where: {user_ids: nil}
--
libgit2 0.21.0