diff --git a/lib/pure/streams.nim b/lib/pure/streams.nim
index 68922f7301..f655a5cd7e 100644
--- a/lib/pure/streams.nim
+++ b/lib/pure/streams.nim
@@ -88,16 +88,18 @@ proc readData*(s: Stream, buffer: pointer, bufLen: int): int =
 
 proc readAll*(s: Stream): string =
   ## Reads all available data.
-  const bufferSize = 1000
+  const bufferSize = 1024
   result = newString(bufferSize)
-  var r = 0
+  var buffer {.noinit.}: array[bufferSize, char]
   while true:
-    let readBytes = readData(s, addr(result[r]), bufferSize)
-    if readBytes < bufferSize:
-      setLen(result, r+readBytes)
+    let readBytes = readData(s, addr(buffer[0]), bufferSize)
+    if readBytes == 0:
+      break
+    let prevLen = result.len
+    result.setLen(prevLen + readBytes)
+    copyMem(addr(result[prevLen]), addr(buffer[0]), readBytes)
+    if readBytes < bufferSize:
       break
-    inc r, bufferSize
-    setLen(result, r+bufferSize)
 
 proc peekData*(s: Stream, buffer: pointer, bufLen: int): int =
   ## low level proc that reads data into an untyped `buffer` of `bufLen` size