diff --git a/src/lib_ffi.c b/src/lib_ffi.c
index 46f27e01..f61fabc0 100644
--- a/src/lib_ffi.c
+++ b/src/lib_ffi.c
@@ -576,7 +576,7 @@ LJLIB_CF(ffi_istype)	LJLIB_REC(.)
       if (ctype_ispointer(ct1->info))
 	b = lj_cconv_compatptr(cts, ct1, ct2, CCF_IGNQUAL);
       else if (ctype_isnum(ct1->info) || ctype_isvoid(ct1->info))
-	b = (((ct1->info ^ ct2->info) & ~CTF_QUAL) == 0);
+	b = (((ct1->info ^ ct2->info) & ~(CTF_QUAL|CTF_LONG)) == 0);
     } else if (ctype_isstruct(ct1->info) && ctype_isptr(ct2->info) &&
 	       ct1 == ctype_rawchild(cts, ct2)) {
       b = 1;