diff --git a/gunicorn/http/message.py b/gunicorn/http/message.py
index 64b2060c0..1f93c7145 100644
--- a/gunicorn/http/message.py
+++ b/gunicorn/http/message.py
@@ -139,7 +139,10 @@ def set_body_reader(self):
             self.body = Body(ChunkedReader(self, self.unreader))
         elif content_length is not None:
             try:
-                content_length = int(content_length)
+                if str(content_length).isnumeric():
+                    content_length = int(content_length)
+                else:
+                    raise InvalidHeader("CONTENT-LENGTH", req=self)
             except ValueError:
                 raise InvalidHeader("CONTENT-LENGTH", req=self)
 
diff --git a/tests/requests/invalid/022.http b/tests/requests/invalid/022.http
new file mode 100644
index 000000000..521c7a06e
--- /dev/null
+++ b/tests/requests/invalid/022.http
@@ -0,0 +1,3 @@
+GET /first HTTP/1.0\r\n
+Content-Length: -0\r\n
+\r\n
\ No newline at end of file
diff --git a/tests/requests/invalid/022.py b/tests/requests/invalid/022.py
new file mode 100644
index 000000000..95b0581ae
--- /dev/null
+++ b/tests/requests/invalid/022.py
@@ -0,0 +1,5 @@
+from gunicorn.config import Config
+from gunicorn.http.errors import InvalidHeader
+
+cfg = Config()
+request = InvalidHeader
diff --git a/tests/requests/invalid/023.http b/tests/requests/invalid/023.http
new file mode 100644
index 000000000..c672f7896
--- /dev/null
+++ b/tests/requests/invalid/023.http
@@ -0,0 +1,3 @@
+GET /first HTTP/1.0\r\n
+Content-Length: 0_1\r\n
+\r\n
\ No newline at end of file
diff --git a/tests/requests/invalid/023.py b/tests/requests/invalid/023.py
new file mode 100644
index 000000000..95b0581ae
--- /dev/null
+++ b/tests/requests/invalid/023.py
@@ -0,0 +1,5 @@
+from gunicorn.config import Config
+from gunicorn.http.errors import InvalidHeader
+
+cfg = Config()
+request = InvalidHeader
diff --git a/tests/requests/invalid/024.http b/tests/requests/invalid/024.http
new file mode 100644
index 000000000..31c062fa9
--- /dev/null
+++ b/tests/requests/invalid/024.http
@@ -0,0 +1,3 @@
+GET /first HTTP/1.0\r\n
+Content-Length: +1\r\n
+\r\n
\ No newline at end of file
diff --git a/tests/requests/invalid/024.py b/tests/requests/invalid/024.py
new file mode 100644
index 000000000..95b0581ae
--- /dev/null
+++ b/tests/requests/invalid/024.py
@@ -0,0 +1,5 @@
+from gunicorn.config import Config
+from gunicorn.http.errors import InvalidHeader
+
+cfg = Config()
+request = InvalidHeader