diff --git a/httpx/_urlparse.py b/httpx/_urlparse.py
index a9a0aecd9b..311e65c90a 100644
--- a/httpx/_urlparse.py
+++ b/httpx/_urlparse.py
@@ -258,16 +258,16 @@ def urlparse(url: str = "", **kwargs: typing.Optional[str]) -> ParseResult:
     # specific component.
 
     # For 'path' we need to drop ? and # from the GEN_DELIMS set.
-    parsed_path: str = quote(path, safe=SUB_DELIMS + ":/[]@")
+    parsed_path: str = quote(path, safe=SUB_DELIMS + ":/[]@%")
     # For 'query' we need to drop '#' from the GEN_DELIMS set.
     # We also exclude '/' because it is more robust to replace it with a percent
     # encoding despite it not being a requirement of the spec.
     parsed_query: typing.Optional[str] = (
-        None if query is None else quote(query, safe=SUB_DELIMS + ":?[]@")
+        None if query is None else quote(query, safe=SUB_DELIMS + ":?[]@%")
     )
     # For 'fragment' we can include all of the GEN_DELIMS set.
     parsed_fragment: typing.Optional[str] = (
-        None if fragment is None else quote(fragment, safe=SUB_DELIMS + ":/?#[]@")
+        None if fragment is None else quote(fragment, safe=SUB_DELIMS + ":/?#[]@%")
     )
 
     # The parsed ASCII bytestrings are our canonical form.
diff --git a/tests/test_urlparse.py b/tests/test_urlparse.py
index b03291b44f..f187210dcc 100644
--- a/tests/test_urlparse.py
+++ b/tests/test_urlparse.py
@@ -150,6 +150,26 @@ def test_param_with_existing_escape_requires_encoding():
     assert str(url) == "http://webservice?u=http%3A%2F%2Fexample.com%3Fq%3Dfoo%252Fa"
 
 
+def test_param_with_existing_escape():
+    url = httpx.URL("https://webservice/?u=/%3D%26&v=1%202")
+    assert str(url) == "https://webservice/?u=%2F%3D%26&v=1%202"
+    assert url.params["u"] == "/=&"
+    assert url.params["v"] == "1 2"
+
+
+def test_param_nested_urls_in_query():
+    src = "special;string with:reserved?cha%20raca/ters&d"
+    data = str(httpx.URL("http://webservice", params={"u": src}))
+    data = str(httpx.URL("http://webservice", params={"u": data}))
+    data = str(httpx.URL("http://webservice", params={"u": data}))
+
+    url = httpx.URL(data)
+    url = httpx.URL(url.params["u"])
+    url = httpx.URL(url.params["u"])
+
+    assert url.params["u"] == src
+
+
 # Tests for invalid URLs
 
 
@@ -260,9 +280,9 @@ def test_copy_with():
 
 def test_path_percent_encoding():
     # Test percent encoding for SUB_DELIMS ALPHA NUM and allowable GEN_DELIMS
-    url = httpx.URL("https://example.com/!$&'()*+,;= abc ABC 123 :/[]@")
-    assert url.raw_path == b"/!$&'()*+,;=%20abc%20ABC%20123%20:/[]@"
-    assert url.path == "/!$&'()*+,;= abc ABC 123 :/[]@"
+    url = httpx.URL("https://example.com/!$&'()*+,;= abc ABC 123 :/[]@%20")
+    assert url.raw_path == b"/!$&'()*+,;=%20abc%20ABC%20123%20:/[]@%20"
+    assert url.path == "/!$&'()*+,;= abc ABC 123 :/[]@ "
     assert url.query == b""
     assert url.fragment == ""
 
@@ -278,8 +298,8 @@ def test_query_percent_encoding():
 
 def test_fragment_percent_encoding():
     # Test percent encoding for SUB_DELIMS ALPHA NUM and allowable GEN_DELIMS
-    url = httpx.URL("https://example.com/#!$&'()*+,;= abc ABC 123 :/[]@" + "?#")
+    url = httpx.URL("https://example.com/#!$&'()*+,;= abc ABC 123 :/[]@%20" + "?#")
     assert url.raw_path == b"/"
     assert url.path == "/"
     assert url.query == b""
-    assert url.fragment == "!$&'()*+,;= abc ABC 123 :/[]@?#"
+    assert url.fragment == "!$&'()*+,;= abc ABC 123 :/[]@ ?#"