diff --git a/doc/src/sgml/spi.sgml b/doc/src/sgml/spi.sgml
index e30d0962ae7..179cceb8da9 100644
--- a/doc/src/sgml/spi.sgml
+++ b/doc/src/sgml/spi.sgml
@@ -2086,7 +2086,7 @@ int SPI_execute_plan_with_paramlist(SPIPlanPtr <parameter>plan</parameter>,
 
  <refsynopsisdiv>
 <synopsis>
-int SPI_execp(SPIPlanPtr <parameter>plan</parameter>, Datum * <parameter>values</parameter>, const char * <parameter>nulls</parameter>, long <parameter>count</parameter>)
+int SPI_execp(SPIPlanPtr <parameter>plan</parameter>, const Datum * <parameter>values</parameter>, const char * <parameter>nulls</parameter>, long <parameter>count</parameter>)
 </synopsis>
  </refsynopsisdiv>
 
@@ -2191,7 +2191,7 @@ int SPI_execp(SPIPlanPtr <parameter>plan</parameter>, Datum * <parameter>values<
  <refsynopsisdiv>
 <synopsis>
 Portal SPI_cursor_open(const char * <parameter>name</parameter>, SPIPlanPtr <parameter>plan</parameter>,
-                       Datum * <parameter>values</parameter>, const char * <parameter>nulls</parameter>,
+                       const Datum * <parameter>values</parameter>, const char * <parameter>nulls</parameter>,
                        bool <parameter>read_only</parameter>)
 </synopsis>
  </refsynopsisdiv>
@@ -4694,7 +4694,7 @@ HeapTupleHeader SPI_returntuple(HeapTuple <parameter>row</parameter>, TupleDesc
  <refsynopsisdiv>
 <synopsis>
 HeapTuple SPI_modifytuple(Relation <parameter>rel</parameter>, HeapTuple <parameter>row</parameter>, int <parameter>ncols</parameter>,
-                          int * <parameter>colnum</parameter>, Datum * <parameter>values</parameter>, const char * <parameter>nulls</parameter>)
+                          int * <parameter>colnum</parameter>, const Datum * <parameter>values</parameter>, const char * <parameter>nulls</parameter>)
 </synopsis>
  </refsynopsisdiv>
 
diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index 52f3b11301c..4e52542a3d1 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -702,7 +702,7 @@ SPI_execute_plan(SPIPlanPtr plan, const Datum *Values, const char *Nulls,
 
 /* Obsolete version of SPI_execute_plan */
 int
-SPI_execp(SPIPlanPtr plan, Datum *Values, const char *Nulls, long tcount)
+SPI_execp(SPIPlanPtr plan, const Datum *Values, const char *Nulls, long tcount)
 {
 	return SPI_execute_plan(plan, Values, Nulls, false, tcount);
 }
@@ -1105,7 +1105,7 @@ SPI_returntuple(HeapTuple tuple, TupleDesc tupdesc)
 
 HeapTuple
 SPI_modifytuple(Relation rel, HeapTuple tuple, int natts, int *attnum,
-				Datum *Values, const char *Nulls)
+				const Datum *Values, const char *Nulls)
 {
 	MemoryContext oldcxt;
 	HeapTuple	mtuple;
@@ -1473,7 +1473,7 @@ Portal
 SPI_cursor_open_with_args(const char *name,
 						  const char *src,
 						  int nargs, Oid *argtypes,
-						  Datum *Values, const char *Nulls,
+						  const Datum *Values, const char *Nulls,
 						  bool read_only, int cursorOptions)
 {
 	Portal		result;
diff --git a/src/include/executor/spi.h b/src/include/executor/spi.h
index f4985cb715d..fd79f86a98c 100644
--- a/src/include/executor/spi.h
+++ b/src/include/executor/spi.h
@@ -119,7 +119,7 @@ extern int	SPI_execute_plan_with_paramlist(SPIPlanPtr plan,
 											ParamListInfo params,
 											bool read_only, long tcount);
 extern int	SPI_exec(const char *src, long tcount);
-extern int	SPI_execp(SPIPlanPtr plan, Datum *Values, const char *Nulls,
+extern int	SPI_execp(SPIPlanPtr plan, const Datum *Values, const char *Nulls,
 					  long tcount);
 extern int	SPI_execute_snapshot(SPIPlanPtr plan,
 								 const Datum *Values, const char *Nulls,
@@ -155,7 +155,7 @@ extern CachedPlan *SPI_plan_get_cached_plan(SPIPlanPtr plan);
 extern HeapTuple SPI_copytuple(HeapTuple tuple);
 extern HeapTupleHeader SPI_returntuple(HeapTuple tuple, TupleDesc tupdesc);
 extern HeapTuple SPI_modifytuple(Relation rel, HeapTuple tuple, int natts,
-								 int *attnum, Datum *Values, const char *Nulls);
+								 int *attnum, const Datum *Values, const char *Nulls);
 extern int	SPI_fnumber(TupleDesc tupdesc, const char *fname);
 extern char *SPI_fname(TupleDesc tupdesc, int fnumber);
 extern char *SPI_getvalue(HeapTuple tuple, TupleDesc tupdesc, int fnumber);
@@ -176,7 +176,7 @@ extern Portal SPI_cursor_open(const char *name, SPIPlanPtr plan,
 extern Portal SPI_cursor_open_with_args(const char *name,
 										const char *src,
 										int nargs, Oid *argtypes,
-										Datum *Values, const char *Nulls,
+										const Datum *Values, const char *Nulls,
 										bool read_only, int cursorOptions);
 extern Portal SPI_cursor_open_with_paramlist(const char *name, SPIPlanPtr plan,
 											 ParamListInfo params, bool read_only);