diff --git a/src/spectator/formatting/failure_block.cr b/src/spectator/formatting/failure_block.cr
index a23979b..23a90a1 100644
--- a/src/spectator/formatting/failure_block.cr
+++ b/src/spectator/formatting/failure_block.cr
@@ -13,26 +13,23 @@ module Spectator::Formatting
   #      # spec/source_spec.cr:42
   # ```
   private struct FailureBlock
-    # Default number of spaces to add for each level of indentation.
-    INDENT_SIZE = 2
-
     # Creates the failure block.
     # The *index* uniquely identifies the failure in the output.
     # The *result* is the outcome of the failed example.
     def initialize(@index : Int32, @result : FailedResult)
-      @indent = 0
     end
 
     # Creates the block of text describing the failure.
     def to_s(io)
+      indent = Indent.new(io)
       inner_indent = integer_length(@index) + 2 # +2 for ) and space after number.
 
-      indent do
-        title(io)
-        indent(inner_indent) do
-          message(io)
-          content(io)
-          source(io)
+      indent.increase do
+        title(indent)
+        indent.increase(inner_indent) do
+          message(indent)
+          content(indent)
+          source(indent)
         end
       end
     end
@@ -42,8 +39,8 @@ module Spectator::Formatting
     # ```text
     # 1) Example name
     # ```
-    private def title(io)
-      line(io, NumberedItem.new(@index, @result.example))
+    private def title(indent)
+      indent.line(NumberedItem.new(@index, @result.example))
     end
 
     # Produces the message line of the failure block.
@@ -53,43 +50,43 @@ module Spectator::Formatting
     # ```
     # The indentation of this line starts directly under
     # the example name from the title line.
-    private def message(io)
-      line(io, FailureMessage.color(@result))
+    private def message(indent)
+      indent.line(FailureMessage.color(@result))
     end
 
     # Produces the main content of the failure block.
     # Any failed expectations are displayed,
     # then an error stacktrace if an error occurred.
-    private def content(io)
-      io.puts
-      indent do
-        unsatisfied_expectations(io)
-        error_stacktrace(io) if @result.is_a?(ErroredResult)
+    private def content(indent)
+      indent.line
+      indent.increase do
+        unsatisfied_expectations(indent)
+        error_stacktrace(indent) if @result.is_a?(ErroredResult)
       end
-      io.puts
+      indent.line
     end
 
     # Produces a list of unsatisfied expectations and their values.
-    private def unsatisfied_expectations(io)
+    private def unsatisfied_expectations(indent)
       @result.expectations.each_unsatisfied do |expectation|
         # TODO: Failure message for this expectation.
-        matcher_values(io, expectation)
+        matcher_values(indent, expectation)
       end
     end
 
     # Produces the values list for an expectation
-    private def matcher_values(io, expectation)
+    private def matcher_values(indent, expectation)
       MatchDataValues.new(expectation.values).each do |pair|
         # TODO: Not all expectations will be failures (color green and red).
-        line(io, Color.failure(pair))
+        indent.line(Color.failure(pair))
       end
     end
 
     # Produces the stack trace for an errored result.
-    private def error_stacktrace(io)
+    private def error_stacktrace(indent)
       error = @result.error
       loop do
-        display_error(io, error)
+        display_error(indent, error)
         if (next_error = error.cause)
           error = next_error
         else
@@ -99,32 +96,18 @@ module Spectator::Formatting
     end
 
     # Display a single error and its stacktrace.
-    private def display_error(io, error) : Nil
-      line(io, Color.error("Caused by: #{error.message} (#{error.class})"))
-      indent do
+    private def display_error(indent, error) : Nil
+      indent.line(Color.error("Caused by: #{error.message} (#{error.class})"))
+      indent.increase do
         error.backtrace.each do |frame|
-          line(io, Color.error(frame))
+          indent.line(Color.error(frame))
         end
       end
     end
 
     # Produces the source line of the failure block.
-    private def source(io)
-      line(io, Comment.color(@result.example.source))
-    end
-
-    # Increases the indentation for a block of text.
-    private def indent(amount = INDENT_SIZE)
-      @indent += amount
-      yield
-    ensure
-      @indent -= amount
-    end
-
-    # Produces a line of text with a leading indent.
-    private def line(io, text)
-      @indent.times { io << ' ' }
-      io.puts text
+    private def source(indent)
+      indent.line(Comment.color(@result.example.source))
     end
 
     # Gets the number of characters a positive integer spans in base 10.