diff --git a/mitmproxy2swagger/test_mitmproxy2swagger.py b/mitmproxy2swagger/test_mitmproxy2swagger.py
index 8c15585..f179be6 100644
--- a/mitmproxy2swagger/test_mitmproxy2swagger.py
+++ b/mitmproxy2swagger/test_mitmproxy2swagger.py
@@ -50,6 +50,24 @@ def test_mitmproxy2swagger_generates_swagger_from_mitmproxy_flow_file_with_form_
     )
 
 
+def test_mitmproxy2swagger_generates_swagger_from_har_file_with_form_data():
+    # Regression test for https://github.com/alufers/mitmproxy2swagger/pull/174
+    # HAR bodies are already decoded strings; calling .decode() on them raised AttributeError
+    data = mitmproxy2swagger_e2e_test(
+        "testdata/form_data_har.har",
+        "https://httpbin.org/",
+    )
+    assert data is not None
+
+    assert (
+        get_nested_key(
+            data,
+            "paths./post.post.requestBody.content.application/x-www-form-urlencoded.schema",
+        )
+        is not None
+    )
+
+
 def test_mitmproxy2swagger_generates_swagger_from_mitmproxy_flow_file_with_generic_keys():
     data = mitmproxy2swagger_e2e_test(
         "testdata/generic_keys_flows",
diff --git a/testdata/form_data_har.har b/testdata/form_data_har.har
new file mode 100644
index 0000000..866bb03
--- /dev/null
+++ b/testdata/form_data_har.har
@@ -0,0 +1,41 @@
+{
+  "log": {
+    "version": "1.2",
+    "creator": { "name": "test", "version": "1.0" },
+    "entries": [
+      {
+        "request": {
+          "method": "POST",
+          "url": "https://httpbin.org/post",
+          "headers": [
+            { "name": "Content-Type", "value": "application/x-www-form-urlencoded" }
+          ],
+          "postData": {
+            "mimeType": "application/x-www-form-urlencoded",
+            "text": "username=alice&password=secret"
+          },
+          "queryString": [],
+          "cookies": [],
+          "headersSize": -1,
+          "bodySize": 29
+        },
+        "response": {
+          "status": 200,
+          "statusText": "OK",
+          "headers": [
+            { "name": "Content-Type", "value": "application/json" }
+          ],
+          "cookies": [],
+          "content": { "size": 2, "mimeType": "application/json", "text": "{}" },
+          "redirectURL": "",
+          "headersSize": -1,
+          "bodySize": 2
+        },
+        "cache": {},
+        "timings": { "send": 0, "wait": 1, "receive": 1 },
+        "startedDateTime": "2024-01-01T00:00:00.000Z",
+        "time": 2
+      }
+    ]
+  }
+}