diff --git a/lib/livebook/file_system/s3.ex b/lib/livebook/file_system/s3.ex
index 5aaabfbdc..387b703cb 100644
--- a/lib/livebook/file_system/s3.ex
+++ b/lib/livebook/file_system/s3.ex
@@ -323,8 +323,7 @@ defimpl Livebook.FileSystem, for: Livebook.FileSystem.S3 do
   defp encode_key(key) do
     key
     |> String.split("/")
-    |> Enum.map(fn segment -> URI.encode(segment, &URI.char_unreserved?/1) end)
-    |> Enum.join("/")
+    |> Enum.map_join("/", fn segment -> URI.encode(segment, &URI.char_unreserved?/1) end)
   end
 
   defp request_response_to_error(error)
diff --git a/lib/livebook/live_markdown/markdown_helpers.ex b/lib/livebook/live_markdown/markdown_helpers.ex
index a4327be20..978505797 100644
--- a/lib/livebook/live_markdown/markdown_helpers.ex
+++ b/lib/livebook/live_markdown/markdown_helpers.ex
@@ -38,9 +38,7 @@ defmodule Livebook.LiveMarkdown.MarkdownHelpers do
   def text_from_ast(ast)
 
   def text_from_ast(ast) when is_list(ast) do
-    ast
-    |> Enum.map(&text_from_ast/1)
-    |> Enum.join("")
+    Enum.map_join(ast, &text_from_ast/1)
   end
 
   def text_from_ast(ast) when is_binary(ast), do: ast
diff --git a/lib/livebook/session.ex b/lib/livebook/session.ex
index e1045cf20..22baff901 100644
--- a/lib/livebook/session.ex
+++ b/lib/livebook/session.ex
@@ -1073,17 +1073,17 @@ defmodule Livebook.Session do
     with {:ok, source_exists?} <- FileSystem.File.exists?(source) do
       if source_exists? do
         with {:ok, destination_exists?} <- FileSystem.File.exists?(images_dir) do
-          if not destination_exists? do
-            # If the directory doesn't exist, we can just change
-            # the directory name, which is more efficient if
-            # available in the given file system
-            FileSystem.File.rename(source, images_dir)
-          else
+          if destination_exists? do
             # If the directory exists, we use copy to place
             # the images there
             with :ok <- FileSystem.File.copy(source, images_dir) do
               FileSystem.File.remove(source)
             end
+          else
+            # If the directory doesn't exist, we can just change
+            # the directory name, which is more efficient if
+            # available in the given file system
+            FileSystem.File.rename(source, images_dir)
           end
         end
       else
diff --git a/lib/livebook_web/helpers/ansi.ex b/lib/livebook_web/helpers/ansi.ex
index 4da7fd1f2..de9a8b799 100644
--- a/lib/livebook_web/helpers/ansi.ex
+++ b/lib/livebook_web/helpers/ansi.ex
@@ -31,9 +31,7 @@ defmodule LivebookWeb.Helpers.ANSI do
   end
 
   defp modifiers_to_css(modifiers) do
-    modifiers
-    |> Enum.map(&modifier_to_css/1)
-    |> Enum.join()
+    Enum.map_join(modifiers, &modifier_to_css/1)
   end
 
   defp modifier_to_css({:font_weight, :bold}), do: "font-weight: 600;"