diff --git a/src/jit/dump.lua b/src/jit/dump.lua
index 746732f9..f296a517 100644
--- a/src/jit/dump.lua
+++ b/src/jit/dump.lua
@@ -552,7 +552,12 @@ local recdepth = 0
 local function fmterr(err, info)
   if type(err) == "number" then
     if type(info) == "function" then info = fmtfunc(info) end
-    err = format(vmdef.traceerr[err], info)
+    local fmt = vmdef.traceerr[err]
+    if fmt == "NYI: bytecode %s" then
+      local oidx = 6 * info
+      info = sub(vmdef.bcnames, oidx+1, oidx+6)
+    end
+    err = format(fmt, info)
   end
   return err
 end
diff --git a/src/jit/v.lua b/src/jit/v.lua
index 8e91f494..45a663d7 100644
--- a/src/jit/v.lua
+++ b/src/jit/v.lua
@@ -62,7 +62,7 @@ local jit = require("jit")
 local jutil = require("jit.util")
 local vmdef = require("jit.vmdef")
 local funcinfo, traceinfo = jutil.funcinfo, jutil.traceinfo
-local type, format = type, string.format
+local type, sub, format = type, string.sub, string.format
 local stdout, stderr = io.stdout, io.stderr
 
 -- Active flag and output file handle.
@@ -89,7 +89,12 @@ end
 local function fmterr(err, info)
   if type(err) == "number" then
     if type(info) == "function" then info = fmtfunc(info) end
-    err = format(vmdef.traceerr[err], info)
+    local fmt = vmdef.traceerr[err]
+    if fmt == "NYI: bytecode %s" then
+      local oidx = 6 * info
+      info = sub(vmdef.bcnames, oidx+1, oidx+6)
+    end
+    err = format(fmt, info)
   end
   return err
 end
diff --git a/src/lj_traceerr.h b/src/lj_traceerr.h
index 19ce30ad..08134dc5 100644
--- a/src/lj_traceerr.h
+++ b/src/lj_traceerr.h
@@ -13,7 +13,7 @@ TREDEF(STACKOV,	"trace too deep")
 TREDEF(SNAPOV,	"too many snapshots")
 TREDEF(BLACKL,	"blacklisted")
 TREDEF(RETRY,	"retry recording")
-TREDEF(NYIBC,	"NYI: bytecode %d")
+TREDEF(NYIBC,	"NYI: bytecode %s")
 
 /* Recording loop ops. */
 TREDEF(LLEAVE,	"leaving loop in root trace")