diff --git a/modules/juce_audio_formats/format/juce_AudioFormatWriter.cpp b/modules/juce_audio_formats/format/juce_AudioFormatWriter.cpp
index 5b91fbc8ab..111f458d92 100644
--- a/modules/juce_audio_formats/format/juce_AudioFormatWriter.cpp
+++ b/modules/juce_audio_formats/format/juce_AudioFormatWriter.cpp
@@ -166,7 +166,7 @@ bool AudioFormatWriter::writeFromFloatArrays (const float* const* channels, int
     if (isFloatingPoint())
         return write ((const int**) channels, numSamples);
 
-    std::vector<int*> chans (256);
+    std::vector<int*> chans (numSourceChannels + 1);
     std::vector<int> scratch (4096);
 
     jassert (numSourceChannels < (int) chans.size());