diff --git a/inputsource.cpp b/inputsource.cpp
index 68addc8..a1538f9 100644
--- a/inputsource.cpp
+++ b/inputsource.cpp
@@ -93,6 +93,10 @@ void InputSource::GetViewport(float *dest, int x, int y, int width, int height,
     fftwf_complex *sample_ptr = &m_data[y * GetFFTStride()];
 
     for (int i = 0; i < height; i++) {
+        // Abort if sampling more data than is actually available
+        if (sample_ptr > m_data + (m_file_size/sizeof(fftwf_complex)))
+            break;
+
         memcpy(m_fftw_in, sample_ptr, m_fft_size * sizeof(fftwf_complex));
 
         // Apply window