diff --git a/Library/Homebrew/cmd/--env.rb b/Library/Homebrew/cmd/--env.rb
index 292bcf866d..0feb338dc8 100644
--- a/Library/Homebrew/cmd/--env.rb
+++ b/Library/Homebrew/cmd/--env.rb
@@ -13,9 +13,8 @@ module Homebrew
     ENV.universal_binary if ARGV.build_universal?
 
     shell_value = ARGV.value("shell")
-    has_plain = ARGV.include?("--plain")
 
-    if has_plain
+    if ARGV.include?("--plain")
       shell = nil
     elsif shell_value.nil?
       # legacy behavior
diff --git a/Library/Homebrew/diagnostic.rb b/Library/Homebrew/diagnostic.rb
index d032ecff5f..86593ff7b6 100644
--- a/Library/Homebrew/diagnostic.rb
+++ b/Library/Homebrew/diagnostic.rb
@@ -496,7 +496,7 @@ module Homebrew
         <<-EOS.undent
           Homebrew's bin was not found in your PATH.
           Consider setting the PATH for example like so
-            #{Utils::Shell.prepend_path_in_shell_profile("#{HOMEBREW_PREFIX}/bin:$PATH")}
+            #{Utils::Shell.prepend_path_in_shell_profile("#{HOMEBREW_PREFIX}/bin")}
         EOS
       end
 
@@ -511,7 +511,7 @@ module Homebrew
           Homebrew's sbin was not found in your PATH but you have installed
           formulae that put executables in #{HOMEBREW_PREFIX}/sbin.
           Consider setting the PATH for example like so
-            #{Utils::Shell.prepend_path_in_shell_profile("#{HOMEBREW_PREFIX}/sbin:$PATH")}
+            #{Utils::Shell.prepend_path_in_shell_profile("#{HOMEBREW_PREFIX}/sbin")}
         EOS
       end
 
diff --git a/Library/Homebrew/test/test_integration_cmds.rb b/Library/Homebrew/test/test_integration_cmds.rb
index 1a5db6b6f3..8801071d22 100644
--- a/Library/Homebrew/test/test_integration_cmds.rb
+++ b/Library/Homebrew/test/test_integration_cmds.rb
@@ -238,7 +238,7 @@ class IntegrationCommandTests < Homebrew::TestCase
   end
 
   def test_env_csh
-    assert_match %r{setenv CMAKE_PREFIX_PATH #{Regexp.quote(HOMEBREW_PREFIX.to_s)}},
+    assert_match %r{setenv CMAKE_PREFIX_PATH #{Regexp.quote(HOMEBREW_PREFIX.to_s)};},
                  cmd("--env", "--shell=tcsh")
   end
 
diff --git a/Library/Homebrew/test/test_shell.rb b/Library/Homebrew/test/test_shell.rb
index 5a10574579..5e054f9d9f 100644
--- a/Library/Homebrew/test/test_shell.rb
+++ b/Library/Homebrew/test/test_shell.rb
@@ -35,4 +35,25 @@ class ShellSmokeTest < Homebrew::TestCase
     assert_equal "\\$", Utils::Shell.csh_quote("$")
     assert_equal "word", Utils::Shell.csh_quote("word")
   end
+
+  def prepend_path_shell(shell, path, fragment)
+    original_shell = ENV["SHELL"]
+    ENV["SHELL"] = shell
+
+    prepend_message = Utils::Shell.prepend_path_in_shell_profile(path)
+    assert(
+      prepend_message.start_with?(fragment),
+      "#{shell}: expected #{prepend_message} to match #{fragment}"
+    )
+
+    ENV["SHELL"] = original_shell
+  end
+
+  def test_prepend_path_in_shell_profile()
+    prepend_path_shell "/bin/tcsh", "/path", "echo 'setenv PATH /path"
+
+    prepend_path_shell "/bin/bash", "/path", "echo 'export PATH=\"/path"
+
+    prepend_path_shell "/usr/local/bin/fish", "/path", "echo 'set -g fish_user_paths \"/path\" $fish_user_paths' >>"
+  end
 end
diff --git a/Library/Homebrew/utils/shell.rb b/Library/Homebrew/utils/shell.rb
index d2301345fa..19e696795f 100644
--- a/Library/Homebrew/utils/shell.rb
+++ b/Library/Homebrew/utils/shell.rb
@@ -10,8 +10,10 @@ module Utils
   }.freeze
 
   module Shell
+    UNSAFE_SHELL_CHAR = /([^A-Za-z0-9_\-.,:\/@\n])/
+
     # take a path and heuristically convert it
-    # to a shell, return nil if there's no match
+    # to a shell name, return nil if there's no match
     def self.path_to_shell(path)
       # we only care about the basename
       shell_name = File.basename(path)
@@ -34,7 +36,8 @@ module Utils
       return "''" if str.empty?
       str = str.dup
       # anything that isn't a known safe character is padded
-      str.gsub!(/([^A-Za-z0-9_\-.,:\/@\n])/, "\\\\" + "\\1")
+      str.gsub!(UNSAFE_SHELL_CHAR, "\\\\" + "\\1")
+      # newlines have to be specially quoted in csh
       str.gsub!(/\n/, "'\\\n'")
       str
     end
@@ -45,7 +48,7 @@ module Utils
       return "''" if str.empty?
       str = str.dup
       # anything that isn't a known safe character is padded
-      str.gsub!(/([^A-Za-z0-9_\-.,:\/@\n])/, "\\\\" + "\\1")
+      str.gsub!(UNSAFE_SHELL_CHAR, "\\\\" + "\\1")
       str.gsub!(/\n/, "'\n'")
       str
     end
@@ -61,7 +64,7 @@ module Utils
         # and a literal \ can be included via \\
         "set -gx #{key} \"#{sh_quote(value)}\""
       when :csh, :tcsh
-        "setenv #{key} #{csh_quote(value)}"
+        "setenv #{key} #{csh_quote(value)};"
       end
     end
 
@@ -72,12 +75,12 @@ module Utils
 
     def self.prepend_path_in_shell_profile(path)
       case preferred_shell 
-      when :bash, :ksh, :sh, :zsh
-        "echo 'export PATH=\"#{sh_quote(path)}:$PATH >> #{shell_profile}"
+      when :bash, :ksh, :sh, :zsh, nil
+        "echo 'export PATH=\"#{sh_quote(path)}:$PATH'\" >> #{shell_profile}"
       when :csh, :tcsh
         "echo 'setenv PATH #{csh_quote(path)}:$PATH' >> #{shell_profile}"
       when :fish
-        "echo 'set -g fish_user_paths $fish_user_paths >> #{sh_quote(path)}' >> #{shell_profile}"
+        "echo 'set -g fish_user_paths \"#{sh_quote(path)}\" $fish_user_paths' >> #{shell_profile}"
       end
     end
   end