diff --git a/packages/http-server/src/server.ts b/packages/http-server/src/server.ts
index bbb9fb0f8..f414f0e32 100644
--- a/packages/http-server/src/server.ts
+++ b/packages/http-server/src/server.ts
@@ -42,9 +42,10 @@ function parseRequestBody(request: IncomingMessage) {
   if (
     // If the body size is null, it means the body itself is null so the promise can resolve with a null value
     request.headers['content-length'] === '0' ||
-    (request.headers['content-type'] === undefined &&
-      request.headers['transfer-encoding'] === undefined &&
-      request.headers['content-length'] === undefined)
+    // Per HTTP 1.1 - these 2 headers are the valid way to indicate that a body exists:
+    // > The presence of a message body in a request is signaled by a Content-Length or Transfer-Encoding header field.
+    // https://httpwg.org/specs/rfc9112.html#message.body
+    (request.headers['transfer-encoding'] === undefined && request.headers['content-length'] === undefined)
   ) {
     return Promise.resolve(null);
   }
diff --git a/packages/http/src/forwarder/errors.ts b/packages/http/src/forwarder/errors.ts
index f331ccc5b..6478bdad5 100644
--- a/packages/http/src/forwarder/errors.ts
+++ b/packages/http/src/forwarder/errors.ts
@@ -5,3 +5,10 @@ export const UPSTREAM_NOT_IMPLEMENTED: Omit<ProblemJson, 'detail'> = {
   title: 'The server does not support the functionality required to fulfill the request',
   status: 501,
 };
+
+export const PROXY_UNSUPPORTED_REQUEST_BODY: Omit<ProblemJson, 'detail'> = {
+  type: 'PROXY_UNSUPPORTED_REQUEST_BODY',
+  title:
+    'The Prism proxy does not support sending a GET/HEAD request with a message body to an upstream server. See: https://github.com/stoplightio/prism/issues/2259',
+  status: 501,
+};
diff --git a/packages/http/src/forwarder/index.ts b/packages/http/src/forwarder/index.ts
index d541fcaba..724eebf31 100644
--- a/packages/http/src/forwarder/index.ts
+++ b/packages/http/src/forwarder/index.ts
@@ -16,7 +16,7 @@ import { parseResponse } from '../utils/parseResponse';
 import { hopByHopHeaders } from './resources';
 import { createUnauthorisedResponse, createUnprocessableEntityResponse } from '../mocker';
 import { ProblemJsonError } from '../types';
-import { UPSTREAM_NOT_IMPLEMENTED } from './errors';
+import { PROXY_UNSUPPORTED_REQUEST_BODY, UPSTREAM_NOT_IMPLEMENTED } from './errors';
 import * as createHttpProxyAgent from 'http-proxy-agent';
 import * as createHttpsProxyAgent from 'https-proxy-agent';
 import { toURLSearchParams } from '../utils/url';
@@ -44,7 +44,7 @@ const forward: IPrismComponents<IHttpOperation, IHttpRequest, IHttpResponse, IHt
           : createUnprocessableEntityResponse(failedValidations);
       }),
       TE.swap,
-      TE.chainEitherK(() => serializeBody(input.body)),
+      TE.chainEitherK(() => serializeBodyForFetch(input, logger)),
       TE.chain(body =>
         TE.tryCatch(async () => {
           const partialUrl = new URL(baseUrl);
@@ -98,13 +98,23 @@ const forward: IPrismComponents<IHttpOperation, IHttpRequest, IHttpResponse, IHt
 
 export default forward;
 
+function serializeBodyForFetch(input: IHttpRequest, logger: Logger): E.Either<Error, string | undefined> {
+  const upperMethod = input.method.toUpperCase();
+  if (['GET', 'HEAD'].includes(upperMethod) && ![null, undefined].includes(input.body as any)) {
+    logger.warn(`Upstream ${upperMethod} call to ${input.url.path} has request body`);
+    return E.left(ProblemJsonError.fromTemplate(PROXY_UNSUPPORTED_REQUEST_BODY));
+  }
+
+  return serializeBody(input.body);
+}
+
 export function serializeBody(body: unknown): E.Either<Error, string | undefined> {
   if (typeof body === 'string') {
     return E.right(body);
   }
-  
+
   if (body) return pipe(J.stringify(body), E.mapLeft(E.toError));
-  
+
   return E.right(undefined);
 }
 
@@ -113,13 +123,13 @@ function logForwardRequest({ logger, url, request }: { logger: Logger; url: stri
   logger.info(`${prefix}Forwarding "${request.method}" request to ${url}...`);
   logRequest({ logger, prefix, ...pick(request, 'body', 'headers') });
 }
-  
+
 function forwardResponseLogger(logger: Logger) {
   return (response: Response) => {
     const prefix = chalk.grey('< ');
-  
+
     logger.info(`${prefix}Received forward response`);
-  
+
     const { status: statusCode } = response;
 
     logResponse({
@@ -127,7 +137,7 @@ function forwardResponseLogger(logger: Logger) {
       statusCode,
       ...pick(response, 'body', 'headers'),
       prefix,
-      });
+    });
 
     return response;
   };
diff --git a/test-harness/specs/proxy/proxy.get-null-body.txt b/test-harness/specs/proxy/proxy.get-null-body.txt
new file mode 100644
index 000000000..92c4885a2
--- /dev/null
+++ b/test-harness/specs/proxy/proxy.get-null-body.txt
@@ -0,0 +1,18 @@
+====test====
+Making a  GET request with a Content-Type header through the proxy server ignores null body
+====spec====
+swagger: "2.0"
+paths:
+  /status/204:
+    get:
+      produces:
+        - text/plain
+      responses:
+        204:
+          description: No Content
+====server====
+proxy -p 4010 ${document} http://httpbin.org
+====command====
+curl -i http://localhost:4010/status/204 -X GET --header 'Content-Type: application/json'
+====expect====
+HTTP/1.1 204 No Content
diff --git a/test-harness/specs/proxy/proxy.get-with-body.txt b/test-harness/specs/proxy/proxy.get-with-body.txt
new file mode 100644
index 000000000..bdc90c7b4
--- /dev/null
+++ b/test-harness/specs/proxy/proxy.get-with-body.txt
@@ -0,0 +1,20 @@
+====test====
+Making a GET request with request body through the proxy server rejects with 501
+====spec====
+swagger: "2.0"
+paths:
+  /status/204:
+    get:
+      produces:
+        - text/plain
+      responses:
+        204:
+          description: No Content
+====server====
+proxy -p 4010 ${document} http://httpbin.org
+====command====
+curl -i http://localhost:4010/status/204 -X GET --header 'Content-Type: application/json' --data '{}'
+====expect====
+HTTP/1.1 501 Not Implemented
+
+{"type":"https://stoplight.io/prism/errors#PROXY_UNSUPPORTED_REQUEST_BODY","title":"The Prism proxy does not support sending a GET/HEAD request with a message body to an upstream server. See: https://github.com/stoplightio/prism/issues/2259","status":501,"detail":""}
\ No newline at end of file