diff --git a/lib/system/sysstr.nim b/lib/system/sysstr.nim
index d445529026..6e3c8722dc 100644
--- a/lib/system/sysstr.nim
+++ b/lib/system/sysstr.nim
@@ -50,12 +50,14 @@ proc rawNewStringNoInit(space: int): NimString {.compilerProc.} =
   if s < 7: s = 7
   result = allocStrNoInit(sizeof(TGenericSeq) + s + 1)
   result.reserved = s
+  result.elemSize = 1
 
 proc rawNewString(space: int): NimString {.compilerProc.} =
   var s = space
   if s < 7: s = 7
   result = allocStr(sizeof(TGenericSeq) + s + 1)
   result.reserved = s
+  result.elemSize = 1
 
 proc mnewString(len: int): NimString {.compilerProc.} =
   result = rawNewString(len)