diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
index 71ae53ff97..1951e93d9d 100644
--- a/src/backend/utils/adt/json.c
+++ b/src/backend/utils/adt/json.c
@@ -180,6 +180,7 @@ datum_to_json_internal(Datum val, bool is_null, StringInfo result,
 {
     char       *outputstr;
     text       *jsontext;
+    int         len;
 
     check_stack_depth();
 
@@ -223,8 +224,8 @@ datum_to_json_internal(Datum val, bool is_null, StringInfo result,
              * Don't call escape_json for a non-key if it's a valid JSON
              * number.
              */
-            if (!key_scalar && IsValidJsonNumber(outputstr, strlen(outputstr)))
-                appendStringInfoString(result, outputstr);
+            if (!key_scalar && IsValidJsonNumber(outputstr, (len = strlen(outputstr))))
+                appendBinaryStringInfo(result, outputstr, len);
             else
                 escape_json(result, outputstr);
             pfree(outputstr);