diff --git a/src/pl/plpython/expected/plpython_spi.out b/src/pl/plpython/expected/plpython_spi.out
index 8853e2540d..26e1cc3c9a 100644
--- a/src/pl/plpython/expected/plpython_spi.out
+++ b/src/pl/plpython/expected/plpython_spi.out
@@ -464,3 +464,29 @@ SELECT plan_composite_args();
  (3,label)
 (1 row)
 
+--
+-- Error cases
+--
+-- Check recovery from a subtransaction start failure; to make one
+-- happen repeatably, try to do a SPI operation in an allegedly
+-- parallel-safe function
+CREATE FUNCTION falsely_marked_parallel_safe() RETURNS SETOF int AS
+$$
+plpy.execute("select 2+2")
+for i in range(0, 5):
+    yield (i)
+$$ LANGUAGE plpython3u parallel safe;
+SET debug_parallel_query = 1;
+SELECT falsely_marked_parallel_safe();
+ERROR:  error fetching next item from iterator
+DETAIL:  spiexceptions.InvalidTransactionState: cannot start subtransactions during a parallel operation
+CONTEXT:  Traceback (most recent call last):
+PL/Python function "falsely_marked_parallel_safe"
+parallel worker
+SELECT falsely_marked_parallel_safe();
+ERROR:  error fetching next item from iterator
+DETAIL:  spiexceptions.InvalidTransactionState: cannot start subtransactions during a parallel operation
+CONTEXT:  Traceback (most recent call last):
+PL/Python function "falsely_marked_parallel_safe"
+parallel worker
+RESET debug_parallel_query;
diff --git a/src/pl/plpython/plpy_cursorobject.c b/src/pl/plpython/plpy_cursorobject.c
index 57e8f8ec21..8bfe05815b 100644
--- a/src/pl/plpython/plpy_cursorobject.c
+++ b/src/pl/plpython/plpy_cursorobject.c
@@ -98,7 +98,8 @@ PLy_cursor_query(const char *query)
 	oldcontext = CurrentMemoryContext;
 	oldowner = CurrentResourceOwner;
 
-	PLy_spi_subtransaction_begin(oldcontext, oldowner);
+	if (!PLy_spi_subtransaction_begin(oldcontext, oldowner))
+		return NULL;
 
 	PG_TRY();
 	{
@@ -196,7 +197,8 @@ PLy_cursor_plan(PyObject *ob, PyObject *args)
 	oldcontext = CurrentMemoryContext;
 	oldowner = CurrentResourceOwner;
 
-	PLy_spi_subtransaction_begin(oldcontext, oldowner);
+	if (!PLy_spi_subtransaction_begin(oldcontext, oldowner))
+		return NULL;
 
 	PG_TRY();
 	{
@@ -333,7 +335,8 @@ PLy_cursor_iternext(PyObject *self)
 	oldcontext = CurrentMemoryContext;
 	oldowner = CurrentResourceOwner;
 
-	PLy_spi_subtransaction_begin(oldcontext, oldowner);
+	if (!PLy_spi_subtransaction_begin(oldcontext, oldowner))
+		return NULL;
 
 	PG_TRY();
 	{
@@ -403,7 +406,8 @@ PLy_cursor_fetch(PyObject *self, PyObject *args)
 	oldcontext = CurrentMemoryContext;
 	oldowner = CurrentResourceOwner;
 
-	PLy_spi_subtransaction_begin(oldcontext, oldowner);
+	if (!PLy_spi_subtransaction_begin(oldcontext, oldowner))
+		return NULL;
 
 	PG_TRY();
 	{
diff --git a/src/pl/plpython/plpy_spi.c b/src/pl/plpython/plpy_spi.c
index 64ca47f218..ca97f2eca6 100644
--- a/src/pl/plpython/plpy_spi.c
+++ b/src/pl/plpython/plpy_spi.c
@@ -77,7 +77,8 @@ PLy_spi_prepare(PyObject *self, PyObject *args)
 	oldcontext = CurrentMemoryContext;
 	oldowner = CurrentResourceOwner;
 
-	PLy_spi_subtransaction_begin(oldcontext, oldowner);
+	if (!PLy_spi_subtransaction_begin(oldcontext, oldowner))
+		return NULL;
 
 	PG_TRY();
 	{
@@ -217,7 +218,8 @@ PLy_spi_execute_plan(PyObject *ob, PyObject *list, long limit)
 	oldcontext = CurrentMemoryContext;
 	oldowner = CurrentResourceOwner;
 
-	PLy_spi_subtransaction_begin(oldcontext, oldowner);
+	if (!PLy_spi_subtransaction_begin(oldcontext, oldowner))
+		return NULL;
 
 	PG_TRY();
 	{
@@ -313,7 +315,8 @@ PLy_spi_execute_query(char *query, long limit)
 	oldcontext = CurrentMemoryContext;
 	oldowner = CurrentResourceOwner;
 
-	PLy_spi_subtransaction_begin(oldcontext, oldowner);
+	if (!PLy_spi_subtransaction_begin(oldcontext, oldowner))
+		return NULL;
 
 	PG_TRY();
 	{
@@ -534,7 +537,9 @@ PLy_rollback(PyObject *self, PyObject *args)
  *	MemoryContext oldcontext = CurrentMemoryContext;
  *	ResourceOwner oldowner = CurrentResourceOwner;
  *
- *	PLy_spi_subtransaction_begin(oldcontext, oldowner);
+ *	if (!PLy_spi_subtransaction_begin(oldcontext, oldowner))
+ *		return NULL;
+ *
  *	PG_TRY();
  *	{
  *		<call SPI functions>
@@ -551,12 +556,38 @@ PLy_rollback(PyObject *self, PyObject *args)
  * These utilities take care of restoring connection to the SPI manager and
  * setting a Python exception in case of an abort.
  */
-void
+bool
 PLy_spi_subtransaction_begin(MemoryContext oldcontext, ResourceOwner oldowner)
 {
-	BeginInternalSubTransaction(NULL);
-	/* Want to run inside function's memory context */
-	MemoryContextSwitchTo(oldcontext);
+	PG_TRY();
+	{
+		/* Start subtransaction (could fail) */
+		BeginInternalSubTransaction(NULL);
+		/* Want to run inside function's memory context */
+		MemoryContextSwitchTo(oldcontext);
+	}
+	PG_CATCH();
+	{
+		ErrorData  *edata;
+
+		/* Save error info */
+		MemoryContextSwitchTo(oldcontext);
+		edata = CopyErrorData();
+		FlushErrorState();
+
+		/* Ensure we restore original context and owner */
+		MemoryContextSwitchTo(oldcontext);
+		CurrentResourceOwner = oldowner;
+
+		/* Make Python raise the exception */
+		PLy_spi_exception_set(edata);
+		FreeErrorData(edata);
+
+		return false;
+	}
+	PG_END_TRY();
+
+	return true;
 }
 
 void
@@ -580,6 +611,8 @@ PLy_spi_subtransaction_abort(MemoryContext oldcontext, ResourceOwner oldowner)
 
 	/* Abort the inner transaction */
 	RollbackAndReleaseCurrentSubTransaction();
+
+	/* Ensure we restore original context and owner */
 	MemoryContextSwitchTo(oldcontext);
 	CurrentResourceOwner = oldowner;
 
diff --git a/src/pl/plpython/plpy_spi.h b/src/pl/plpython/plpy_spi.h
index 98ccd21093..a43d803928 100644
--- a/src/pl/plpython/plpy_spi.h
+++ b/src/pl/plpython/plpy_spi.h
@@ -22,7 +22,7 @@ typedef struct PLyExceptionEntry
 } PLyExceptionEntry;
 
 /* handling of SPI operations inside subtransactions */
-extern void PLy_spi_subtransaction_begin(MemoryContext oldcontext, ResourceOwner oldowner);
+extern bool PLy_spi_subtransaction_begin(MemoryContext oldcontext, ResourceOwner oldowner);
 extern void PLy_spi_subtransaction_commit(MemoryContext oldcontext, ResourceOwner oldowner);
 extern void PLy_spi_subtransaction_abort(MemoryContext oldcontext, ResourceOwner oldowner);
 
diff --git a/src/pl/plpython/sql/plpython_spi.sql b/src/pl/plpython/sql/plpython_spi.sql
index fcd113acaa..69a448cd68 100644
--- a/src/pl/plpython/sql/plpython_spi.sql
+++ b/src/pl/plpython/sql/plpython_spi.sql
@@ -320,3 +320,22 @@ SELECT cursor_fetch_next_empty();
 SELECT cursor_plan();
 SELECT cursor_plan_wrong_args();
 SELECT plan_composite_args();
+
+--
+-- Error cases
+--
+
+-- Check recovery from a subtransaction start failure; to make one
+-- happen repeatably, try to do a SPI operation in an allegedly
+-- parallel-safe function
+CREATE FUNCTION falsely_marked_parallel_safe() RETURNS SETOF int AS
+$$
+plpy.execute("select 2+2")
+for i in range(0, 5):
+    yield (i)
+$$ LANGUAGE plpython3u parallel safe;
+
+SET debug_parallel_query = 1;
+SELECT falsely_marked_parallel_safe();
+SELECT falsely_marked_parallel_safe();
+RESET debug_parallel_query;