diff --git a/.gitignore b/.gitignore
index bedc02b47f..05579c2c25 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,6 +11,7 @@
 /Library/Homebrew/.npmignore
 /Library/Homebrew/bin
 /Library/Homebrew/doc
+/Library/Homebrew/prof
 /Library/Homebrew/test/.gem
 /Library/Homebrew/test/.subversion
 /Library/Homebrew/test/coverage
diff --git a/Library/Homebrew/brew.rb b/Library/Homebrew/brew.rb
index 5ca3ee4f0c..d9fd4d2a3e 100644
--- a/Library/Homebrew/brew.rb
+++ b/Library/Homebrew/brew.rb
@@ -2,6 +2,7 @@
 # frozen_string_literal: true
 
 if ENV["HOMEBREW_STACKPROF"]
+  require "rubygems"
   require "stackprof"
   StackProf.start(mode: :wall, raw: true)
 end
diff --git a/Library/Homebrew/dev-cmd/prof.rb b/Library/Homebrew/dev-cmd/prof.rb
index dfc7f1ae18..4a1f5e5ae0 100644
--- a/Library/Homebrew/dev-cmd/prof.rb
+++ b/Library/Homebrew/dev-cmd/prof.rb
@@ -37,7 +37,9 @@ module Homebrew
       output_filename = "prof/d3-flamegraph.html"
       safe_system "stackprof --d3-flamegraph prof/stackprof.dump > #{output_filename}"
     else
-      Homebrew.install_gem_setup_path! "ruby-prof"
+      # NOTE: ruby-prof v1.4.3 is the last version that supports Ruby 2.6.x
+      # TODO: Remove explicit version arg when we move to a newer version of Ruby
+      Homebrew.install_gem_setup_path! "ruby-prof", version: "1.4.3"
       output_filename = "prof/call_stack.html"
       safe_system "ruby-prof", "--printer=call_stack", "--file=#{output_filename}", brew_rb, "--", *args.named
     end
diff --git a/Library/Homebrew/test/dev-cmd/prof_spec.rb b/Library/Homebrew/test/dev-cmd/prof_spec.rb
index c8a62801ae..cdbe09687d 100644
--- a/Library/Homebrew/test/dev-cmd/prof_spec.rb
+++ b/Library/Homebrew/test/dev-cmd/prof_spec.rb
@@ -5,4 +5,24 @@ require "cmd/shared_examples/args_parse"
 
 describe "brew prof" do
   it_behaves_like "parseable arguments"
+
+  describe "integration tests", :integration_test, :needs_network do
+    after do
+      FileUtils.rm_rf HOMEBREW_LIBRARY_PATH/"prof"
+    end
+
+    it "works using ruby-prof (the default)" do
+      expect { brew "prof", "help", "HOMEBREW_BROWSER" => "echo" }
+        .to output(/^Example usage:/).to_stdout
+        .and not_to_output.to_stderr
+        .and be_a_success
+    end
+
+    it "works using stackprof" do
+      expect { brew "prof", "--stackprof", "help", "HOMEBREW_BROWSER" => "echo" }
+        .to output(/^Example usage:/).to_stdout
+        .and not_to_output.to_stderr
+        .and be_a_success
+    end
+  end
 end