diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9eeb5b8..d071ac2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+## 4.0.3 [unreleased]
+
+- Added warnings for certain regular expressions
+- Fixed anchored regular expressions
+
 ## 4.0.2
 
 - Added block form of `scroll`
diff --git a/lib/searchkick/query.rb b/lib/searchkick/query.rb
index 81007f2..7226312 100644
--- a/lib/searchkick/query.rb
+++ b/lib/searchkick/query.rb
@@ -985,7 +985,20 @@ module Searchkick
       elsif value.nil?
         {bool: {must_not: {exists: {field: field}}}}
       elsif value.is_a?(Regexp)
-        {regexp: {field => {value: value.source, flags: "NONE"}}}
+        if value.casefold?
+          warn "[searchkick] Case-insensitive flag does not work with Elasticsearch"
+        end
+
+        source = value.source
+        unless source.start_with?("\\A") && source.end_with?("\\z")
+          # https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-regexp-query.html
+          warn "[searchkick] Regular expressions are always anchored in Elasticsearch"
+        end
+
+        # remove \A and \z
+        source = source.sub(/\\A/, "").sub(/\\z\z/, "")
+
+        {regexp: {field => {value: source, flags: "NONE"}}}
       else
         {term: {field => value}}
       end
diff --git a/test/where_test.rb b/test/where_test.rb
index 4a157a4..ef196e1 100644
--- a/test/where_test.rb
+++ b/test/where_test.rb
@@ -78,7 +78,7 @@ class WhereTest < Minitest::Test
 
   def test_regexp
     store_names ["Product A"]
-    assert_search "*", ["Product A"], where: {name: /Pro.+/}
+    assert_search "*", ["Product A"], where: {name: /\APro.+\z/}
   end
 
   def test_alternate_regexp
@@ -88,7 +88,22 @@ class WhereTest < Minitest::Test
 
   def test_special_regexp
     store_names ["Product <A>", "Item <B>"]
-    assert_search "*", ["Product <A>"], where: {name: /Pro.+<.+/}
+    assert_search "*", ["Product <A>"], where: {name: /\APro.+<.+\z/}
+  end
+
+  # regular expressions are always anchored in ES
+  def test_regexp_not_anchored
+    store_names ["abcde"]
+    assert_search "*", [], where: {name: /abcd/}
+    assert_search "*", ["abcde"], where: {name: /abcde/}
+    assert_search "*", ["abcde"], where: {name: /\Aabcde\z/}
+  end
+
+  def test_regexp_case
+    store_names ["abcde"]
+    assert_search "*", [], where: {name: /\AABCDE\z/}
+    # flags don't work
+    assert_search "*", [], where: {name: /\AABCDE\z/i}
   end
 
   def test_prefix
--
libgit2 0.21.0