diff --git a/pyproject.toml b/pyproject.toml
index de53856..f7f687a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -45,11 +45,11 @@ dependencies = [
     "urllib3>=1.12",
 ]
 optional-dependencies.diazo = [
-    "diazo>=1.0.5",
+    "diazo==1.5.0",
     "lxml>=3.4",
 ]
 optional-dependencies.tests = [
-    "diazo",
+    "diazo==1.5.0",
     "lxml>=3.4",
     "coverage",
     "flake8",
diff --git a/revproxy/views.py b/revproxy/views.py
index 3298d46..6d8dd21 100644
--- a/revproxy/views.py
+++ b/revproxy/views.py
@@ -10,12 +10,12 @@
 
 try:
     from django.utils.six.moves.urllib.parse import (
-        urlparse, urlencode, quote_plus, quote
+        urlparse, quote_plus, quote, parse_qsl
     )
 except ImportError:
     # Django 3 has no six
     from urllib.parse import (
-        urlparse, urlencode, quote_plus, quote
+        urlparse, quote_plus, quote, parse_qsl
     )
 
 from django.conf import settings
@@ -27,7 +27,7 @@
 from .exceptions import InvalidUpstream
 from .response import get_django_response
 from .transformer import DiazoTransformer
-from .utils import normalize_request_headers, encode_items
+from .utils import normalize_request_headers
 
 # Chars that don't need to be quoted. We use same than nginx:
 #   https://github.com/nginx/nginx/blob/nginx-1.9/src/core/ngx_string.c
@@ -176,8 +176,15 @@ def get_quoted_path(self, path):
 
     def get_encoded_query_params(self):
         """Return encoded query params to be used in proxied request"""
-        get_data = encode_items(self.request.GET.lists())
-        return urlencode(get_data)
+        params = parse_qsl(
+            self.request.GET.urlencode(),
+            keep_blank_values=True,
+        )
+        custom_query = '&'.join(
+            k if v == '' else f'{k}={v}'
+            for k, v in params
+        )
+        return custom_query
 
     def _created_proxy_response(self, request, path):
         request_payload = request.body
diff --git a/tests/test_views.py b/tests/test_views.py
index 1ccddfb..34259e8 100644
--- a/tests/test_views.py
+++ b/tests/test_views.py
@@ -256,3 +256,30 @@ def get_proxy_request_headers(self, request):
                                         preload_content=False,
                                         decode_content=False,
                                         headers=custom_headers)
+
+    def test_raw_query_string_is_preserved_for_flag_params(self):
+        """
+        Regression test: preserve "flag" params (no '=') when proxying.
+
+        Example: `...?. . .&c` must NOT become `...&c=`.
+        """
+        class CustomProxyView(ProxyView):
+            upstream = 'http://example.com'
+
+        raw_qs = 'q=1&a=2&c'
+        path = 'some/path'
+
+        # Important: set QUERY_STRING explicitly so Django keeps it in request.META
+        request = self.factory.get(path, QUERY_STRING=raw_qs)
+        CustomProxyView.as_view()(request, path)
+
+        url = 'http://example.com/' + path + '?' + raw_qs
+        headers = {u'Cookie': u''}
+        self.urlopen.assert_called_with('GET',
+                                        url,
+                                        body=b'',
+                                        redirect=False,
+                                        retries=None,
+                                        preload_content=False,
+                                        decode_content=False,
+                                        headers=headers)