diff --git a/vcr/filters.py b/vcr/filters.py
index 7f33155..f2d389a 100644
--- a/vcr/filters.py
+++ b/vcr/filters.py
@@ -113,7 +113,10 @@ def replace_post_data_parameters(request, replacements):
                 if sep is None:
                     new_splits.append((k, sep, ov))
                 else:
-                    rk = k.decode("utf-8")
+                    try:
+                        rk = k.decode("utf-8")
+                    except UnicodeDecodeError:
+                        rk = k
                     if rk not in replacements:
                         new_splits.append((k, sep, ov))
                     else:
diff --git a/vcr/stubs/httpx_stubs.py b/vcr/stubs/httpx_stubs.py
index 65d56cf..d57a433 100644
--- a/vcr/stubs/httpx_stubs.py
+++ b/vcr/stubs/httpx_stubs.py
@@ -106,7 +106,12 @@ def _from_serialized_response(request, serialized_response, history=None):
 
 
 def _make_vcr_request(httpx_request, **kwargs):
-    body = httpx_request.read().decode("utf-8")
+    body_bytes = httpx_request.read()
+    try:
+        body = body_bytes.decode("utf-8")
+    except UnicodeDecodeError:
+        body = body_bytes
+
     uri = str(httpx_request.url)
     headers = dict(httpx_request.headers)
     return VcrRequest(httpx_request.method, uri, body, headers)