diff --git a/sentry_sdk/utils.py b/sentry_sdk/utils.py
index 4fa78bdb64..170774354e 100644
--- a/sentry_sdk/utils.py
+++ b/sentry_sdk/utils.py
@@ -734,15 +734,50 @@ def realign_remark(remark):
     )
 
 
-HAS_REAL_CONTEXTVARS = True
+def _is_threading_local_monkey_patched():
+    # type: () -> bool
+    try:
+        from gevent.monkey import is_object_patched  # type: ignore
+
+        if is_object_patched("_threading", "local"):
+            return True
+    except ImportError:
+        pass
+
+    try:
+        from eventlet.patcher import is_monkey_patched  # type: ignore
+
+        if is_monkey_patched("thread"):
+            return True
+    except ImportError:
+        pass
+
+    return False
+
 
-try:
-    from contextvars import ContextVar  # type: ignore
+IS_THREADING_LOCAL_MONKEY_PATCHED = _is_threading_local_monkey_patched()
+del _is_threading_local_monkey_patched
 
-    if not PY2 and sys.version_info < (3, 7):
-        import aiocontextvars  # type: ignore  # noqa
-except ImportError:
-    HAS_REAL_CONTEXTVARS = False
+
+def _get_contextvars():
+    # () -> (bool, Type)
+    """
+    Try to import contextvars and use it if it's deemed safe. We should not use
+    contextvars if gevent or eventlet have patched thread locals, as
+    contextvars are unaffected by that patch.
+
+    https://github.com/gevent/gevent/issues/1407
+    """
+    if not IS_THREADING_LOCAL_MONKEY_PATCHED:
+        try:
+            from contextvars import ContextVar  # type: ignore
+
+            if not PY2 and sys.version_info < (3, 7):
+                import aiocontextvars  # type: ignore  # noqa
+
+            return True, ContextVar
+        except ImportError:
+            pass
 
     from threading import local
 
@@ -759,6 +794,12 @@ def get(self, default):
         def set(self, value):
             setattr(self._local, "value", value)
 
+    return False, ContextVar
+
+
+HAS_REAL_CONTEXTVARS, ContextVar = _get_contextvars()
+del _get_contextvars
+
 
 def transaction_from_function(func):
     # type: (Callable[..., Any]) -> Optional[str]
diff --git a/tox.ini b/tox.ini
index af53b4914d..47243e9081 100644
--- a/tox.ini
+++ b/tox.ini
@@ -27,7 +27,7 @@ envlist =
     {pypy,py2.7,py3.5,py3.6,py3.7,py3.8}-falcon-1.4
     {pypy,py2.7,py3.5,py3.6,py3.7,py3.8}-falcon-2.0
 
-    {py3.5,py3.6,py3.7}-sanic-{0.8,18,19}
+    {py3.5,py3.6,py3.7}-sanic-{0.8,18}
 
     {pypy,py2.7,py3.5,py3.6,py3.7,py3.8}-celery-{4.1,4.2,4.3}
     {pypy,py2.7}-celery-3
@@ -79,7 +79,6 @@ deps =
 
     sanic-0.8: sanic>=0.8,<0.9
     sanic-18: sanic>=18.0,<19.0
-    sanic-19: sanic>=19.0,<20.0
     {py3.5,py3.6}-sanic: aiocontextvars==0.2.1
     sanic: aiohttp