diff --git a/BufferedTextOutput.cpp b/BufferedTextOutput.cpp
index 3c7db8b..1b340a3 100644
--- a/BufferedTextOutput.cpp
+++ b/BufferedTextOutput.cpp
@@ -52,15 +52,15 @@
     }
 
     status_t append(const char* txt, size_t len) {
+        if (len > SIZE_MAX - bufferPos) return NO_MEMORY; // overflow
         if ((len+bufferPos) > bufferSize) {
+            if ((len + bufferPos) > SIZE_MAX / 3) return NO_MEMORY; // overflow
             size_t newSize = ((len+bufferPos)*3)/2;
-            if (newSize < (len+bufferPos)) return NO_MEMORY;  // overflow
             void* b = realloc(buffer, newSize);
             if (!b) return NO_MEMORY;
             buffer = (char*)b;
             bufferSize = newSize;
         }
-        if ((len+bufferPos) < bufferPos) return NO_MEMORY;  // integer overflow
         memcpy(buffer+bufferPos, txt, len);
         bufferPos += len;
         return NO_ERROR;