diff --git a/news/3763.bugfix b/news/3763.bugfix
new file mode 100644
index 000000000..18741c232
--- /dev/null
+++ b/news/3763.bugfix
@@ -0,0 +1 @@
+Keep install options in requirements.txt from leaking.
diff --git a/src/pip/_internal/req/req_install.py b/src/pip/_internal/req/req_install.py
index 889fe1d39..8d4f9ef46 100644
--- a/src/pip/_internal/req/req_install.py
+++ b/src/pip/_internal/req/req_install.py
@@ -771,11 +771,13 @@ class InstallRequirement(object):
         # Options specified in requirements file override those
         # specified on the command line, since the last option given
         # to setup.py is the one that is used.
-        global_options += self.options.get('global_options', [])
-        install_options += self.options.get('install_options', [])
+        global_options = list(global_options) + \
+            self.options.get('global_options', [])
+        install_options = list(install_options) + \
+            self.options.get('install_options', [])
 
         if self.isolated:
-            global_options = list(global_options) + ["--no-user-cfg"]
+            global_options = global_options + ["--no-user-cfg"]
 
         with TempDirectory(kind="record") as temp_dir:
             record_filename = os.path.join(temp_dir.path, 'install-record.txt')
diff --git a/tests/functional/test_install_reqs.py b/tests/functional/test_install_reqs.py
index b867f8fc4..003b37fb8 100644
--- a/tests/functional/test_install_reqs.py
+++ b/tests/functional/test_install_reqs.py
@@ -513,3 +513,37 @@ def test_install_unsupported_wheel_file(script, data):
     assert ("simple.dist-0.1-py1-none-invalid.whl is not a supported " +
             "wheel on this platform" in result.stderr)
     assert len(result.files_created) == 0
+
+
+def test_install_options_local_to_package(script, data, virtualenv):
+    """Make sure --install-options does not leak across packages.
+
+    A requirements.txt file can have per-package --install-options; these
+    should be isolated to just the package instead of leaking to subsequent
+    packages.  This needs to be a functional test because the bug was around
+    cross-contamination at install time.
+    """
+    home_simple = script.scratch_path.join("for-simple")
+    test_simple = script.scratch.join("for-simple")
+    home_simple.mkdir()
+    reqs_file = script.scratch_path.join("reqs.txt")
+    reqs_file.write(
+          textwrap.dedent("""
+              simple --install-option='--home=%s'
+              INITools
+              """ % home_simple))
+    result = script.pip(
+            'install',
+            '--no-index', '-f', data.find_links,
+            '-r', reqs_file,
+            expect_error=True,
+    )
+
+    simple = test_simple / 'lib' / 'python' / 'simple'
+    bad = test_simple / 'lib' / 'python' / 'initools'
+    good = script.site_packages / 'initools'
+    assert simple in result.files_created
+    assert result.files_created[simple].dir
+    assert bad not in result.files_created
+    assert good in result.files_created
+    assert result.files_created[good].dir