diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index 5756365c8f..11ca800e4c 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -36,10 +36,16 @@
 #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.
+ */
 uint64		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;
@@ -132,6 +138,10 @@ SPI_connect_ext(int options)
 	_SPI_current->queryEnv = NULL;
 	_SPI_current->atomic = (options & SPI_OPT_NONATOMIC ? false : true);
 	_SPI_current->internal_xact = false;
+	_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
@@ -154,6 +164,15 @@ SPI_connect_ext(int options)
 	/* ... 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;
 }
 
@@ -176,12 +195,13 @@ 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;
 
 	/* Exit stack level */
 	_SPI_connected--;
@@ -274,9 +294,11 @@ SPICleanup(void)
 {
 	_SPI_current = NULL;
 	_SPI_connected = -1;
+	/* Reset API global variables, too */
 	SPI_processed = 0;
 	SPI_lastoid = InvalidOid;
 	SPI_tuptable = NULL;
+	SPI_result = 0;
 }
 
 /*
@@ -336,18 +358,20 @@ 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--;
 		if (_SPI_connected < 0)
 			_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 401fd998f7..0da3a41050 100644
--- a/src/include/executor/spi_priv.h
+++ b/src/include/executor/spi_priv.h
@@ -42,6 +42,12 @@ typedef struct
 								 * transactions */
 	bool		internal_xact;	/* SPI-managed transaction boundary, skip
 								 * cleanup */
+
+	/* saved values of API global variables for previous nesting level */
+	uint64		outer_processed;
+	Oid			outer_lastoid;
+	SPITupleTable *outer_tuptable;
+	int			outer_result;
 } _SPI_connection;
 
 /*