diff --git a/extended_query_builder.go b/extended_query_builder.go
index 51759362..5d03790e 100644
--- a/extended_query_builder.go
+++ b/extended_query_builder.go
@@ -15,7 +15,7 @@ type extendedQueryBuilder struct {
 }
 
 func (eqb *extendedQueryBuilder) AppendParam(m *pgtype.Map, oid uint32, arg interface{}) error {
-	f := chooseParameterFormatCode(m, oid, arg)
+	f := eqb.chooseParameterFormatCode(m, oid, arg)
 	eqb.paramFormats = append(eqb.paramFormats, f)
 
 	v, err := eqb.encodeExtendedParamValue(m, oid, f, arg)
@@ -100,3 +100,15 @@ func (eqb *extendedQueryBuilder) encodeExtendedParamValue(m *pgtype.Map, oid uin
 	}
 	return nil, SerializationError(fmt.Sprintf("Cannot encode %T into oid %v - %T must implement Encoder or be converted to a string", arg, oid, arg))
 }
+
+// chooseParameterFormatCode determines the correct format code for an
+// argument to a prepared statement. It defaults to TextFormatCode if no
+// determination can be made.
+func (eqb *extendedQueryBuilder) chooseParameterFormatCode(m *pgtype.Map, oid uint32, arg interface{}) int16 {
+	switch arg.(type) {
+	case string, *string:
+		return TextFormatCode
+	}
+
+	return m.FormatCodeForOID(oid)
+}
diff --git a/values.go b/values.go
index 67363986..7d1933b1 100644
--- a/values.go
+++ b/values.go
@@ -143,18 +143,6 @@ func encodePreparedStatementArgument(m *pgtype.Map, buf []byte, oid uint32, arg
 	return nil, SerializationError(fmt.Sprintf("Cannot encode %T into oid %v - %T must implement Encoder or be converted to a string", arg, oid, arg))
 }
 
-// chooseParameterFormatCode determines the correct format code for an
-// argument to a prepared statement. It defaults to TextFormatCode if no
-// determination can be made.
-func chooseParameterFormatCode(m *pgtype.Map, oid uint32, arg interface{}) int16 {
-	switch arg.(type) {
-	case string, *string:
-		return TextFormatCode
-	}
-
-	return m.FormatCodeForOID(oid)
-}
-
 func stripNamedType(val *reflect.Value) (interface{}, bool) {
 	switch val.Kind() {
 	case reflect.Int: