diff --git a/aiohttp/client_reqrep.py b/aiohttp/client_reqrep.py
index 22f0e077f64..25160f198bc 100644
--- a/aiohttp/client_reqrep.py
+++ b/aiohttp/client_reqrep.py
@@ -78,6 +78,7 @@
 
 _CONNECTION_CLOSED_EXCEPTION = ClientConnectionError("Connection closed")
 _CONTAINS_CONTROL_CHAR_RE = re.compile(r"[^-!#$%&'*+.^_`|~0-9a-zA-Z]")
+_DIGITS_RE = re.compile(r"\d+", re.ASCII)
 
 
 def _gen_default_accept_encoding() -> str:
@@ -753,12 +754,9 @@ def _get_content_length(self) -> int | None:
             return None
 
         content_length_hdr = self.headers[hdrs.CONTENT_LENGTH]
-        try:
-            return int(content_length_hdr)
-        except ValueError:
-            raise ValueError(
-                f"Invalid Content-Length header: {content_length_hdr}"
-            ) from None
+        if not _DIGITS_RE.fullmatch(content_length_hdr):
+            raise ValueError(f"Invalid Content-Length header: {content_length_hdr!r}")
+        return int(content_length_hdr)
 
     @property
     def _writer(self) -> asyncio.Task[None] | None:
diff --git a/tests/test_client_request.py b/tests/test_client_request.py
index 751deaa8f18..6cd617a1674 100644
--- a/tests/test_client_request.py
+++ b/tests/test_client_request.py
@@ -1822,7 +1822,24 @@ async def test_get_content_length(make_client_request: _RequestMaker) -> None:
 
     # Invalid Content-Length header
     req.headers["Content-Length"] = "invalid"
-    with pytest.raises(ValueError, match="Invalid Content-Length header: invalid"):
+    with pytest.raises(ValueError, match="Invalid Content-Length header"):
+        req._get_content_length()
+
+
+async def test_get_content_length_invalid_formats(
+    make_client_request: _RequestMaker,
+) -> None:
+    req = make_client_request("get", URL("http://python.org/"))
+
+    req.headers["Content-Length"] = "100"
+    assert req._get_content_length() == 100
+
+    req.headers["Content-Length"] = "-100"
+    with pytest.raises(ValueError, match="Invalid Content-Length header"):
+        req._get_content_length()
+
+    req.headers["Content-Length"] = "५"  # Devengali number 5
+    with pytest.raises(ValueError, match="Invalid Content-Length header"):
         req._get_content_length()