diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index 1332e76b044..fdd9317bfac 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -35,10 +35,16 @@
 #include "utils/typcache.h"
 
 
+/*
+ * These global variables are part of the API for various SPI functions
+ * (a horrible API choice, but it's too late now).  To reduce the risk of
+ * interference between different SPI callers, we save and restore them
+ * when entering/exiting a SPI nesting level.
+ */
 uint32		SPI_processed = 0;
 Oid			SPI_lastoid = InvalidOid;
 SPITupleTable *SPI_tuptable = NULL;
-int			SPI_result;
+int			SPI_result = 0;
 
 static _SPI_connection *_SPI_stack = NULL;
 static _SPI_connection *_SPI_current = NULL;
@@ -130,6 +136,10 @@ SPI_connect(void)
 	_SPI_current->procCxt = NULL;		/* in case we fail to create 'em */
 	_SPI_current->execCxt = NULL;
 	_SPI_current->connectSubid = GetCurrentSubTransactionId();
+	_SPI_current->outer_processed = SPI_processed;
+	_SPI_current->outer_lastoid = SPI_lastoid;
+	_SPI_current->outer_tuptable = SPI_tuptable;
+	_SPI_current->outer_result = SPI_result;
 
 	/*
 	 * Create memory contexts for this procedure
@@ -152,6 +162,15 @@ SPI_connect(void)
 	/* ... and switch to procedure's context */
 	_SPI_current->savedcxt = MemoryContextSwitchTo(_SPI_current->procCxt);
 
+	/*
+	 * Reset API global variables so that current caller cannot accidentally
+	 * depend on state of an outer caller.
+	 */
+	SPI_processed = 0;
+	SPI_lastoid = InvalidOid;
+	SPI_tuptable = NULL;
+	SPI_result = 0;
+
 	return SPI_OK_CONNECT;
 }
 
@@ -174,12 +193,13 @@ SPI_finish(void)
 	_SPI_current->procCxt = NULL;
 
 	/*
-	 * Reset result variables, especially SPI_tuptable which is probably
+	 * Restore outer API variables, especially SPI_tuptable which is probably
 	 * pointing at a just-deleted tuptable
 	 */
-	SPI_processed = 0;
-	SPI_lastoid = InvalidOid;
-	SPI_tuptable = NULL;
+	SPI_processed = _SPI_current->outer_processed;
+	SPI_lastoid = _SPI_current->outer_lastoid;
+	SPI_tuptable = _SPI_current->outer_tuptable;
+	SPI_result = _SPI_current->outer_result;
 
 	/*
 	 * After _SPI_begin_call _SPI_connected == _SPI_curid. Now we are closing
@@ -216,9 +236,11 @@ AtEOXact_SPI(bool isCommit)
 	_SPI_current = _SPI_stack = NULL;
 	_SPI_stack_depth = 0;
 	_SPI_connected = _SPI_curid = -1;
+	/* Reset API global variables, too */
 	SPI_processed = 0;
 	SPI_lastoid = InvalidOid;
 	SPI_tuptable = NULL;
+	SPI_result = 0;
 }
 
 /*
@@ -256,19 +278,21 @@ AtEOSubXact_SPI(bool isCommit, SubTransactionId mySubid)
 		}
 
 		/*
-		 * Pop the stack entry and reset global variables.  Unlike
+		 * Restore outer global variables and pop the stack entry.  Unlike
 		 * SPI_finish(), we don't risk switching to memory contexts that might
 		 * be already gone.
 		 */
+		SPI_processed = connection->outer_processed;
+		SPI_lastoid = connection->outer_lastoid;
+		SPI_tuptable = connection->outer_tuptable;
+		SPI_result = connection->outer_result;
+
 		_SPI_connected--;
 		_SPI_curid = _SPI_connected;
 		if (_SPI_connected == -1)
 			_SPI_current = NULL;
 		else
 			_SPI_current = &(_SPI_stack[_SPI_connected]);
-		SPI_processed = 0;
-		SPI_lastoid = InvalidOid;
-		SPI_tuptable = NULL;
 	}
 
 	if (found && isCommit)
diff --git a/src/include/executor/spi_priv.h b/src/include/executor/spi_priv.h
index 1ca095b02b5..2dffbe9b980 100644
--- a/src/include/executor/spi_priv.h
+++ b/src/include/executor/spi_priv.h
@@ -31,6 +31,12 @@ typedef struct
 	MemoryContext execCxt;		/* executor context */
 	MemoryContext savedcxt;		/* context of SPI_connect's caller */
 	SubTransactionId connectSubid;		/* ID of connecting subtransaction */
+
+	/* saved values of API global variables for previous nesting level */
+	uint32		outer_processed;
+	Oid			outer_lastoid;
+	SPITupleTable *outer_tuptable;
+	int			outer_result;
 } _SPI_connection;
 
 /*