diff --git a/src/parser.c b/src/parser.c
index 59312446da..ebc6ff4966 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -312,7 +312,7 @@ static jv check_object_key(block k) {
     char errbuf[15];
     return jv_string_fmt("Cannot use %s (%s) as object key",
         jv_kind_name(block_const_kind(k)),
-        jv_dump_string_trunc(jv_copy(block_const(k)), errbuf, sizeof(errbuf)));
+        jv_dump_string_trunc(block_const(k), errbuf, sizeof(errbuf)));
   }
   return jv_invalid();
 }
diff --git a/src/parser.y b/src/parser.y
index bc39892390..89348e985c 100644
--- a/src/parser.y
+++ b/src/parser.y
@@ -172,7 +172,7 @@ static jv check_object_key(block k) {
     char errbuf[15];
     return jv_string_fmt("Cannot use %s (%s) as object key",
         jv_kind_name(block_const_kind(k)),
-        jv_dump_string_trunc(jv_copy(block_const(k)), errbuf, sizeof(errbuf)));
+        jv_dump_string_trunc(block_const(k), errbuf, sizeof(errbuf)));
   }
   return jv_invalid();
 }