diff --git a/src/python.cpp b/src/python.cpp
index 652c09bd1..310398fab 100644
--- a/src/python.cpp
+++ b/src/python.cpp
@@ -661,6 +661,11 @@ SEXP py_fetch_error(bool maybe_reuse_cached_r_trace) {
 
   PyObject *excType, *excValue, *excTraceback;
   PyErr_Fetch(&excType, &excValue, &excTraceback);  // we now own the PyObjects
+
+  if (!excType) {
+    Rcpp::stop("Unknown Python error.");
+  }
+
   PyErr_NormalizeException(&excType, &excValue, &excTraceback);
 
   if (excTraceback != NULL && excValue != NULL && s_isPython3) {