diff --git a/src/backend/utils/adt/regproc.c b/src/backend/utils/adt/regproc.c
index 37817583d35..637b94d4002 100644
--- a/src/backend/utils/adt/regproc.c
+++ b/src/backend/utils/adt/regproc.c
@@ -35,6 +35,7 @@
 #include "lib/stringinfo.h"
 #include "miscadmin.h"
 #include "parser/parse_type.h"
+#include "parser/scansup.h"
 #include "utils/builtins.h"
 #include "utils/fmgroids.h"
 #include "utils/lsyscache.h"
@@ -1436,7 +1437,7 @@ parseNameAndArgTypes(const char *string, bool allowNone, List **names,
 	ptr2 = ptr + strlen(ptr);
 	while (--ptr2 > ptr)
 	{
-		if (!isspace((unsigned char) *ptr2))
+		if (!scanner_isspace(*ptr2))
 			break;
 	}
 	if (*ptr2 != ')')
@@ -1453,7 +1454,7 @@ parseNameAndArgTypes(const char *string, bool allowNone, List **names,
 	for (;;)
 	{
 		/* allow leading whitespace */
-		while (isspace((unsigned char) *ptr))
+		while (scanner_isspace(*ptr))
 			ptr++;
 		if (*ptr == '\0')
 		{
@@ -1509,7 +1510,7 @@ parseNameAndArgTypes(const char *string, bool allowNone, List **names,
 		/* Lop off trailing whitespace */
 		while (--ptr2 >= typename)
 		{
-			if (!isspace((unsigned char) *ptr2))
+			if (!scanner_isspace(*ptr2))
 				break;
 			*ptr2 = '\0';
 		}
diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index f990877ffb7..dd9ae471108 100644
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -2362,7 +2362,7 @@ SplitIdentifierString(char *rawstring, char separator,
 
 	*namelist = NIL;
 
-	while (isspace((unsigned char) *nextp))
+	while (scanner_isspace(*nextp))
 		nextp++;				/* skip leading whitespace */
 
 	if (*nextp == '\0')
@@ -2400,7 +2400,7 @@ SplitIdentifierString(char *rawstring, char separator,
 
 			curname = nextp;
 			while (*nextp && *nextp != separator &&
-				   !isspace((unsigned char) *nextp))
+				   !scanner_isspace(*nextp))
 				nextp++;
 			endp = nextp;
 			if (curname == nextp)
@@ -2422,13 +2422,13 @@ SplitIdentifierString(char *rawstring, char separator,
 			pfree(downname);
 		}
 
-		while (isspace((unsigned char) *nextp))
+		while (scanner_isspace(*nextp))
 			nextp++;			/* skip trailing whitespace */
 
 		if (*nextp == separator)
 		{
 			nextp++;
-			while (isspace((unsigned char) *nextp))
+			while (scanner_isspace(*nextp))
 				nextp++;		/* skip leading whitespace for next */
 			/* we expect another name, so done remains false */
 		}
@@ -2487,7 +2487,7 @@ SplitDirectoriesString(char *rawstring, char separator,
 
 	*namelist = NIL;
 
-	while (isspace((unsigned char) *nextp))
+	while (scanner_isspace(*nextp))
 		nextp++;				/* skip leading whitespace */
 
 	if (*nextp == '\0')
@@ -2524,7 +2524,7 @@ SplitDirectoriesString(char *rawstring, char separator,
 			while (*nextp && *nextp != separator)
 			{
 				/* trailing whitespace should not be included in name */
-				if (!isspace((unsigned char) *nextp))
+				if (!scanner_isspace(*nextp))
 					endp = nextp + 1;
 				nextp++;
 			}
@@ -2532,13 +2532,13 @@ SplitDirectoriesString(char *rawstring, char separator,
 				return false;	/* empty unquoted name not allowed */
 		}
 
-		while (isspace((unsigned char) *nextp))
+		while (scanner_isspace(*nextp))
 			nextp++;			/* skip trailing whitespace */
 
 		if (*nextp == separator)
 		{
 			nextp++;
-			while (isspace((unsigned char) *nextp))
+			while (scanner_isspace(*nextp))
 				nextp++;		/* skip leading whitespace for next */
 			/* we expect another name, so done remains false */
 		}