diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 22815bc9ad..be0d602508 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -5377,7 +5377,8 @@ int PQclientEncoding(const PGconn *<replaceable>conn</replaceable>);
 </synopsis>
 
       Note that it returns the encoding ID, not a symbolic string
-      such as <literal>EUC_JP</literal>. To convert an encoding ID to an encoding name, you
+      such as <literal>EUC_JP</literal>. If unsuccessful, it returns -1.
+      To convert an encoding ID to an encoding name, you
       can use:
 
 <synopsis>
diff --git a/src/backend/utils/mb/wchar.c b/src/backend/utils/mb/wchar.c
index 6d03a10854..5f65f1bc89 100644
--- a/src/backend/utils/mb/wchar.c
+++ b/src/backend/utils/mb/wchar.c
@@ -1778,10 +1778,7 @@ pg_mic_mblen(const unsigned char *mbstr)
 int
 pg_encoding_mblen(int encoding, const char *mbstr)
 {
-	Assert(PG_VALID_ENCODING(encoding));
-
-	return ((encoding >= 0 &&
-			 encoding < sizeof(pg_wchar_table) / sizeof(pg_wchar_tbl)) ?
+	return (PG_VALID_ENCODING(encoding) ?
 		((*pg_wchar_table[encoding].mblen) ((const unsigned char *) mbstr)) :
 	((*pg_wchar_table[PG_SQL_ASCII].mblen) ((const unsigned char *) mbstr)));
 }
@@ -1792,10 +1789,7 @@ pg_encoding_mblen(int encoding, const char *mbstr)
 int
 pg_encoding_dsplen(int encoding, const char *mbstr)
 {
-	Assert(PG_VALID_ENCODING(encoding));
-
-	return ((encoding >= 0 &&
-			 encoding < sizeof(pg_wchar_table) / sizeof(pg_wchar_tbl)) ?
+	return (PG_VALID_ENCODING(encoding) ?
 	   ((*pg_wchar_table[encoding].dsplen) ((const unsigned char *) mbstr)) :
 	((*pg_wchar_table[PG_SQL_ASCII].dsplen) ((const unsigned char *) mbstr)));
 }
@@ -1808,12 +1802,9 @@ pg_encoding_dsplen(int encoding, const char *mbstr)
 int
 pg_encoding_verifymb(int encoding, const char *mbstr, int len)
 {
-	Assert(PG_VALID_ENCODING(encoding));
-
-	return ((encoding >= 0 &&
-			 encoding < sizeof(pg_wchar_table) / sizeof(pg_wchar_tbl)) ?
-			((*pg_wchar_table[encoding].mbverify) ((const unsigned char *) mbstr, len)) :
-			((*pg_wchar_table[PG_SQL_ASCII].mbverify) ((const unsigned char *) mbstr, len)));
+	return (PG_VALID_ENCODING(encoding) ?
+		((*pg_wchar_table[encoding].mbverify) ((const unsigned char *) mbstr, len)) :
+	((*pg_wchar_table[PG_SQL_ASCII].mbverify) ((const unsigned char *) mbstr, len)));
 }
 
 /*