diff --git a/lib/system/sysstr.nim b/lib/system/sysstr.nim
index 326c601bda..e4673b169e 100644
--- a/lib/system/sysstr.nim
+++ b/lib/system/sysstr.nim
@@ -82,7 +82,8 @@ proc copyStr(s: NimString, start: int): NimString {.compilerProc.} =
 proc toNimStr(str: cstring, len: int): NimString {.compilerProc.} =
   result = rawNewStringNoInit(len)
   result.len = len
-  c_memcpy(result.data, str, len + 1)
+  c_memcpy(result.data, str, len)
+  result[result.len] = '\0'
 
 proc cstrToNimstr(str: cstring): NimString {.compilerRtl.} =
   result = toNimStr(str, c_strlen(str))