diff --git a/app/logical/post_query_builder.rb b/app/logical/post_query_builder.rb
index 0788186d2..565943576 100644
--- a/app/logical/post_query_builder.rb
+++ b/app/logical/post_query_builder.rb
@@ -718,7 +718,7 @@ class PostQueryBuilder
     class_methods do
       def scan_query(query)
         terms = []
-        query = query.gsub(/[[:space:]]/, " ")
+        query = query.to_s.gsub(/[[:space:]]/, " ")
         scanner = StringScanner.new(query)
 
         until scanner.eos?
diff --git a/test/unit/post_query_builder_test.rb b/test/unit/post_query_builder_test.rb
index 50a7592f3..c293cfe47 100644
--- a/test/unit/post_query_builder_test.rb
+++ b/test/unit/post_query_builder_test.rb
@@ -63,12 +63,21 @@ class PostQueryBuilderTest < ActiveSupport::TestCase
       assert_tag_match([post1], "?")
     end
 
+    should "return posts for the empty search" do
+      post1 = create(:post)
+
+      assert_tag_match([post1], "")
+      assert_tag_match([post1], " ")
+      assert_tag_match([post1], nil)
+    end
+
     should "return posts for 1 tag" do
       post1 = create(:post, tag_string: "aaa")
       post2 = create(:post, tag_string: "aaa bbb")
       post3 = create(:post, tag_string: "bbb ccc")
 
       assert_tag_match([post2, post1], "aaa")
+      assert_tag_match([post2, post1], " aaa ")
     end
 
     should "return posts for a 2 tag join" do
@@ -77,6 +86,7 @@ class PostQueryBuilderTest < ActiveSupport::TestCase
       post3 = create(:post, tag_string: "bbb ccc")
 
       assert_tag_match([post2], "aaa bbb")
+      assert_tag_match([post2], " aaa bbb ")
     end
 
     should "return posts for a 2 tag union" do