diff --git a/bedevere/__main__.py b/bedevere/__main__.py
index 2ea53e49..2ea16b17 100644
--- a/bedevere/__main__.py
+++ b/bedevere/__main__.py
@@ -37,7 +37,7 @@ async def main(request):
                                       cache=cache)
             # Give GitHub some time to reach internal consistency.
             await asyncio.sleep(1)
-            await router.dispatch(event, gh)
+            await router.dispatch(event, gh, session=session)
         try:
             print('GH requests remaining:', gh.rate_limit.remaining)
         except AttributeError:
diff --git a/bedevere/bpo.py b/bedevere/bpo.py
index 51a7afba..e1014a36 100644
--- a/bedevere/bpo.py
+++ b/bedevere/bpo.py
@@ -21,13 +21,6 @@
 SKIP_ISSUE_LABEL = util.skip_label("issue")
 STATUS_CONTEXT = "bedevere/issue-number"
 # Try to keep descriptions at or below 50 characters, else GitHub's CSS will truncate it.
-_FAILURE_DESCRIPTION = 'No issue # in title or "skip issue" label found'
-_FAILURE_URL = "https://devguide.python.org/pullrequest/#submitting"
-FAILURE_STATUS = util.create_status(STATUS_CONTEXT, util.StatusState.FAILURE,
-                                    description=_FAILURE_DESCRIPTION,
-                                    target_url=_FAILURE_URL)
-del _FAILURE_DESCRIPTION
-del _FAILURE_URL
 SKIP_ISSUE_STATUS = util.create_status(STATUS_CONTEXT, util.StatusState.SUCCESS,
                                        description="Issue report skipped")
 
@@ -35,21 +28,26 @@
 @router.register("pull_request", action="opened")
 @router.register("pull_request", action="synchronize")
 @router.register("pull_request", action="reopened")
-async def set_status(event, gh, *args, **kwargs):
+async def set_status(event, gh, session=None, *args, **kwargs):
     """Set the issue number status on the pull request."""
     issue_number_found = ISSUE_RE.search(event.data["pull_request"]["title"])
     if not issue_number_found:
         issue = await util.issue_for_PR(gh, event.data["pull_request"])
-        status = SKIP_ISSUE_STATUS if util.skip("issue", issue) else FAILURE_STATUS
+        status = (SKIP_ISSUE_STATUS if util.skip("issue", issue)
+                                    else create_failure_status_no_issue())
     else:
-        if "body" in event.data["pull_request"]:
-            body = event.data["pull_request"]["body"] or ""
-            if not body or CLOSING_TAG not in body:
-                issue_number = issue_number_found.group("issue")
-                new_body = BODY.format(body=body, issue_number=issue_number)
-                body_data = {"body": new_body}
-                await gh.patch(event.data["pull_request"]["url"], data=body_data)
-        status = create_success_status(issue_number_found)
+        issue_number = issue_number_found.group("issue")
+        issue_number_on_bpo = await _validate_issue_number(issue_number, session=session)
+        if issue_number_on_bpo:
+            if "body" in event.data["pull_request"]:
+                body = event.data["pull_request"]["body"] or ""
+                if not body or CLOSING_TAG not in body:
+                    new_body = BODY.format(body=body, issue_number=issue_number)
+                    body_data = {"body": new_body}
+                    await gh.patch(event.data["pull_request"]["url"], data=body_data)
+            status = create_success_status(issue_number)
+        else:
+            status = create_failure_status_issue_not_on_bpo(issue_number)
     await util.post_status(gh, event, status)
 
 
@@ -68,7 +66,7 @@ async def new_label(event, gh, *args, **kwargs):
         issue_number_found = ISSUE_RE.search(
             event.data["pull_request"]["title"])
         if issue_number_found:
-            status = create_success_status(issue_number_found)
+            status = create_success_status(issue_number_found.group("issue"))
         else:
             status = SKIP_ISSUE_STATUS
         await util.post_status(gh, event, status)
@@ -104,15 +102,32 @@ async def hyperlink_bpo_text(event, gh, *args, **kwargs):
             await gh.patch(event.data[event_name][body_location], data=body_data)
 
 
-def create_success_status(found_issue):
+def create_success_status(issue_number):
     """Create a success status for when an issue number was found in the title."""
-    issue_number = found_issue.group("issue")
     url = f"https://bugs.python.org/issue{issue_number}"
     return util.create_status(STATUS_CONTEXT, util.StatusState.SUCCESS,
                               description=f"Issue number {issue_number} found",
                               target_url=url)
 
 
+def create_failure_status_issue_not_on_bpo(issue_number):
+    """Create a failure status for when an issue does not exist on the bug tracker."""
+    description = f"Issue #{issue_number} not found on bugs.python.org"
+    url = f"https://bugs.python.org/issue{issue_number}"
+    return util.create_status(STATUS_CONTEXT, util.StatusState.FAILURE,
+                              description=description,
+                              target_url=url)
+
+
+def create_failure_status_no_issue():
+    """Create a failure status for when no issue number was found in the title."""
+    description = 'No issue # in title or "skip issue" label found'
+    url = "https://devguide.python.org/pullrequest/#submitting"
+    return util.create_status(STATUS_CONTEXT, util.StatusState.FAILURE,
+                              description=description,
+                              target_url=url)
+
+
 def check_hyperlink(match):
     """The span checking of regex matches takes care of cases like bpo-123 [bpo-123]…"""
     issue = match.group("issue")
@@ -155,3 +170,10 @@ def create_hyperlink_in_comment_body(body):
             leftover_body = leftover_body[presence:]
     new_body = new_body + leftover_body
     return new_body
+
+
+async def _validate_issue_number(issue_number, session):
+    """Make sure the issue number exists on bugs.python.org."""
+    url = f"https://bugs.python.org/issue{issue_number}"
+    async with session.head(url) as res:
+        return res.status != 404
diff --git a/dev-requirements.txt b/dev-requirements.txt
index e74e58d2..a1d13800 100644
--- a/dev-requirements.txt
+++ b/dev-requirements.txt
@@ -1,4 +1,5 @@
 -r requirements.txt
+asynctest==0.13.0
 pytest==5.0.1
 pytest-asyncio==0.10.0
 pytest-aiohttp==0.3.0
diff --git a/tests/test_bpo.py b/tests/test_bpo.py
index df8efe4b..1d3402a7 100644
--- a/tests/test_bpo.py
+++ b/tests/test_bpo.py
@@ -1,3 +1,5 @@
+import aiohttp
+import asynctest
 import pytest
 
 from gidgethub import sansio
@@ -27,7 +29,9 @@ async def patch(self, url, data):
 
 @pytest.mark.asyncio
 @pytest.mark.parametrize("action", ["opened", "synchronize", "reopened"])
-async def test_set_status_failure(action):
+async def test_set_status_failure(action, monkeypatch):
+    monkeypatch.setattr(bpo, '_validate_issue_number',
+                        asynctest.CoroutineMock(return_value=True))
     data = {
         "action": action,
         "pull_request": {
@@ -48,11 +52,35 @@ async def test_set_status_failure(action):
     assert status["state"] == "failure"
     assert status["target_url"].startswith("https://devguide.python.org")
     assert status["context"] == "bedevere/issue-number"
+    bpo._validate_issue_number.assert_not_awaited()
 
 
 @pytest.mark.asyncio
 @pytest.mark.parametrize("action", ["opened", "synchronize", "reopened"])
-async def test_set_status_success(action):
+async def test_set_status_failure_via_issue_not_found_on_bpo(action):
+    data = {
+        "action": action,
+        "pull_request": {
+             "statuses_url": "https://api.github.com/blah/blah/git-sha",
+            "title": "bpo-123: Invalid issue number",
+        },
+    }
+    event = sansio.Event(data, event="pull_request", delivery_id="12345")
+    gh = FakeGH()
+    async with aiohttp.ClientSession() as session:
+        await bpo.router.dispatch(event, gh, session=session)
+    status = gh.data
+    assert status["state"] == "failure"
+    assert status["target_url"].startswith("https://bugs.python.org")
+    assert status["context"] == "bedevere/issue-number"
+    assert status["description"] == "Issue #123 not found on bugs.python.org"
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("action", ["opened", "synchronize", "reopened"])
+async def test_set_status_success(action, monkeypatch):
+    monkeypatch.setattr(bpo, '_validate_issue_number',
+                        asynctest.CoroutineMock(return_value=True))
     data = {
         "action": action,
         "pull_request": {
@@ -69,11 +97,36 @@ async def test_set_status_success(action):
     assert "1234" in status["description"]
     assert status["context"] == "bedevere/issue-number"
     assert "git-sha" in gh.url
+    bpo._validate_issue_number.assert_awaited_with("1234", session=None)
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("action", ["opened", "synchronize", "reopened"])
+async def test_set_status_success_issue_found_on_bpo(action):
+    data = {
+        "action": action,
+        "pull_request": {
+            "statuses_url": "https://api.github.com/blah/blah/git-sha",
+            "title": "bpo-12345: an issue!",
+        },
+    }
+    event = sansio.Event(data, event="pull_request", delivery_id="12345")
+    gh = FakeGH()
+    async with aiohttp.ClientSession() as session:
+        await bpo.router.dispatch(event, gh, session=session)
+    status = gh.data
+    assert status["state"] == "success"
+    assert status["target_url"].endswith("issue12345")
+    assert "12345" in status["description"]
+    assert status["context"] == "bedevere/issue-number"
+    assert "git-sha" in gh.url
 
 
 @pytest.mark.asyncio
 @pytest.mark.parametrize("action", ["opened", "synchronize", "reopened"])
-async def test_set_status_success_via_skip_issue_label(action):
+async def test_set_status_success_via_skip_issue_label(action, monkeypatch):
+    monkeypatch.setattr(bpo, '_validate_issue_number',
+                        asynctest.CoroutineMock(return_value=True))
     data = {
         "action": action,
         "pull_request": {
@@ -94,10 +147,13 @@ async def test_set_status_success_via_skip_issue_label(action):
     assert status["state"] == "success"
     assert status["context"] == "bedevere/issue-number"
     assert "git-sha" in gh.url
+    bpo._validate_issue_number.assert_not_awaited()
 
 
 @pytest.mark.asyncio
-async def test_edit_title():
+async def test_edit_title(monkeypatch):
+    monkeypatch.setattr(bpo, '_validate_issue_number',
+                        asynctest.CoroutineMock(return_value=True))
     data = {
         "pull_request": {
             "statuses_url": "https://api.github.com/blah/blah/git-sha",
@@ -110,10 +166,13 @@ async def test_edit_title():
     gh = FakeGH()
     await bpo.router.dispatch(event, gh)
     assert gh.data is not None
+    bpo._validate_issue_number.assert_awaited_with("1234", session=None)
 
 
 @pytest.mark.asyncio
-async def test_no_body_when_edit_title():
+async def test_no_body_when_edit_title(monkeypatch):
+    monkeypatch.setattr(bpo, '_validate_issue_number',
+                        asynctest.CoroutineMock(return_value=True))
     data = {
         "action": "edited",
         "pull_request": {
@@ -131,10 +190,13 @@ async def test_no_body_when_edit_title():
     await bpo.router.dispatch(event, gh)
     assert gh.patch_data is not None
     assert gh.patch_data["body"] == "\n\n<!-- issue-number: bpo-32636 -->\nhttps://bugs.python.org/issue32636\n<!-- /issue-number -->\n"
+    bpo._validate_issue_number.assert_awaited_with("32636", session=None)
 
 
 @pytest.mark.asyncio
-async def test_edit_other_than_title():
+async def test_edit_other_than_title(monkeypatch):
+    monkeypatch.setattr(bpo, '_validate_issue_number',
+                        asynctest.CoroutineMock(return_value=True))
     data = {
         "pull_request": {
             "statuses_url": "https://api.github.com/blah/blah/git-sha",
@@ -147,6 +209,7 @@ async def test_edit_other_than_title():
     gh = FakeGH()
     await bpo.router.dispatch(event, gh)
     assert gh.data is None
+    bpo._validate_issue_number.assert_not_awaited()
 
 
 @pytest.mark.asyncio
@@ -203,9 +266,11 @@ async def test_new_label_not_skip_issue():
 
 
 @pytest.mark.asyncio
-async def test_removed_label_from_label_deletion():
+async def test_removed_label_from_label_deletion(monkeypatch):
     """When a label is completely deleted from a repo, it triggers an 'unlabeled'
     event, but the payload has no details about the removed label."""
+    monkeypatch.setattr(bpo, '_validate_issue_number',
+                        asynctest.CoroutineMock(return_value=True))
     data = {
         "action": "unlabeled",
         # No "label" key.
@@ -218,10 +283,13 @@ async def test_removed_label_from_label_deletion():
     gh = FakeGH()
     await bpo.router.dispatch(event, gh)
     assert gh.data is None
+    bpo._validate_issue_number.assert_not_awaited()
 
 
 @pytest.mark.asyncio
-async def test_removed_label_skip_issue():
+async def test_removed_label_skip_issue(monkeypatch):
+    monkeypatch.setattr(bpo, '_validate_issue_number',
+                        asynctest.CoroutineMock(return_value=True))
     data = {
         "action": "unlabeled",
         "label": {"name": "skip issue"},
@@ -239,10 +307,13 @@ async def test_removed_label_skip_issue():
     assert "1234" in status["description"]
     assert status["context"] == "bedevere/issue-number"
     assert "git-sha" in gh.url
+    bpo._validate_issue_number.assert_awaited_with("1234", session=None)
 
 
 @pytest.mark.asyncio
-async def test_removed_label_non_skip_issue():
+async def test_removed_label_non_skip_issue(monkeypatch):
+    monkeypatch.setattr(bpo, '_validate_issue_number',
+                        asynctest.CoroutineMock(return_value=True))
     data = {
         "action": "unlabeled",
         "label": {"name": "non-trivial"},
@@ -254,10 +325,13 @@ async def test_removed_label_non_skip_issue():
     gh = FakeGH()
     await bpo.router.dispatch(event, gh)
     assert gh.data is None
+    bpo._validate_issue_number.assert_not_awaited()
 
 
 @pytest.mark.asyncio
-async def test_set_body_success():
+async def test_set_body_success(monkeypatch):
+    monkeypatch.setattr(bpo, '_validate_issue_number',
+                        asynctest.CoroutineMock(return_value=True))
     data = {
         "action": "opened",
         "pull_request": {
@@ -273,10 +347,13 @@ async def test_set_body_success():
     status = gh.patch_data
     assert "https://bugs.python.org/issue1234" in status["body"]
     assert "1347" in gh.patch_url
+    bpo._validate_issue_number.assert_awaited_with("1234", session=None)
 
 
 @pytest.mark.asyncio
-async def test_set_body_failure():
+async def test_set_body_failure(monkeypatch):
+    monkeypatch.setattr(bpo, '_validate_issue_number',
+                        asynctest.CoroutineMock(return_value=True))
     data = {
         "action": "opened",
         "pull_request": {
@@ -291,11 +368,24 @@ async def test_set_body_failure():
     await bpo.router.dispatch(event, gh)
     assert gh.patch_data is None
     assert gh.patch_url is None
+    bpo._validate_issue_number.assert_awaited_with("1234", session=None)
 
 
 @pytest.mark.asyncio
-@pytest.mark.parametrize("action", ["opened", "edited"])
-async def test_set_pull_request_body_success(action):
+async def test_set_pull_request_body_success_opened(monkeypatch):
+    await set_pull_request_body_success_helper("opened", monkeypatch)
+    bpo._validate_issue_number.assert_awaited_with("12345", session=None)
+
+
+@pytest.mark.asyncio
+async def test_set_pull_request_body_success_edited(monkeypatch):
+    await set_pull_request_body_success_helper("edited", monkeypatch)
+    bpo._validate_issue_number.assert_not_awaited()
+
+
+async def set_pull_request_body_success_helper(action, monkeypatch):
+    monkeypatch.setattr(bpo, '_validate_issue_number',
+                        asynctest.CoroutineMock(return_value=True))
     data = {
         "action": action,
         "pull_request": {
@@ -315,6 +405,7 @@ async def test_set_pull_request_body_success(action):
     assert "[bpo-12345](https://bugs.python.org/issue12345)" in body_data["body"]
     assert "123456" in gh.patch_url
 
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize("event,action", [("issue_comment", "created"),
                                           ("issue_comment", "edited"),
@@ -336,9 +427,12 @@ async def test_set_comment_body_success(event, action):
     assert "[bpo-12345](https://bugs.python.org/issue12345)" in body_data["body"]
     assert "123456" in gh.patch_url
 
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize("action", ["opened", "edited"])
-async def test_set_pull_request_body_without_bpo(action):
+async def test_set_pull_request_body_without_bpo(action, monkeypatch):
+    monkeypatch.setattr(bpo, '_validate_issue_number',
+                        asynctest.CoroutineMock(return_value=True))
     data = {
         "action": action,
         "pull_request": {
@@ -356,6 +450,7 @@ async def test_set_pull_request_body_without_bpo(action):
     await bpo.router.dispatch(event, gh)
     if gh.patch_data:
         assert "[bpo-123](https://bugs.python.org/issue123)" not in gh.patch_data
+        bpo._validate_issue_number.assert_awaited_with("12345", session=None)
 
 
 @pytest.mark.asyncio
@@ -380,8 +475,26 @@ async def test_set_comment_body_without_bpo(event, action):
 
 
 @pytest.mark.asyncio
-@pytest.mark.parametrize("action", ["opened", "edited"])
-async def test_set_pull_request_body_already_hyperlinked_bpo(action):
+async def test_set_pull_request_body_already_hyperlinked_bpo_opened(monkeypatch):
+    await set_pull_request_body_already_hyperlinked_bpo_helper(
+        "opened",
+        monkeypatch
+    )
+    bpo._validate_issue_number.assert_awaited_with("12345", session=None)
+
+
+@pytest.mark.asyncio
+async def test_set_pull_request_body_already_hyperlinked_bpo_edited(monkeypatch):
+    await set_pull_request_body_already_hyperlinked_bpo_helper(
+        "edited",
+        monkeypatch
+    )
+    bpo._validate_issue_number.assert_not_awaited()
+
+
+async def set_pull_request_body_already_hyperlinked_bpo_helper(action, monkeypatch):
+    monkeypatch.setattr(bpo, '_validate_issue_number',
+                        asynctest.CoroutineMock(return_value=True))
     data = {
         "action": action,
         "pull_request": {