diff --git a/inputsource.cpp b/inputsource.cpp
index d92b332..24500e3 100644
--- a/inputsource.cpp
+++ b/inputsource.cpp
@@ -29,8 +29,11 @@ InputSource::~InputSource() {
     fclose(m_file);
 }
 
-bool InputSource::getSamples(fftwf_complex *dest, int start, int length)
+bool InputSource::getSamples(fftwf_complex *dest, off_t start, int length)
 {
+    if(start < 0 || length < 0)
+        return false;
+
     if (start + length >= sampleCount)
         return false;
 
diff --git a/inputsource.h b/inputsource.h
index 1118d10..34eb49e 100644
--- a/inputsource.h
+++ b/inputsource.h
@@ -16,6 +16,6 @@ public:
     InputSource(const char *filename);
     ~InputSource();
 
-    bool getSamples(fftwf_complex *dest, int start, int length);
+    bool getSamples(fftwf_complex *dest, off_t start, int length);
     off_t getSampleCount() { return sampleCount; };
 };
diff --git a/spectrogram.cpp b/spectrogram.cpp
index 6d544f0..d4c5f10 100644
--- a/spectrogram.cpp
+++ b/spectrogram.cpp
@@ -61,7 +61,7 @@ void Spectrogram::paintEvent(QPaintEvent *event)
 
 	if (inputSource != nullptr) {
 		int height = rect.height();
-		int y = rect.y();
+		off_t y = rect.y();
 
 		QImage image(fftSize, height, QImage::Format_RGB32);
 
@@ -216,7 +216,7 @@ int Spectrogram::getStride()
 	return fftSize / pow(2, zoomLevel);
 }
 
-off_t Spectrogram::lineToSample(int line) {
+off_t Spectrogram::lineToSample(off_t line) {
 	return line * getStride();
 }
 
diff --git a/spectrogram.h b/spectrogram.h
index f49d835..6a2a17e 100644
--- a/spectrogram.h
+++ b/spectrogram.h
@@ -55,7 +55,7 @@ private:
 	float* getFFTTile(off_t tile);
 	void getLine(float *dest, off_t sample);
 	void paintTimeAxis(QPainter *painter, QRect rect);
-	off_t lineToSample(int line);
+	off_t lineToSample(off_t line);
 	int sampleToLine(off_t sample);
 	QString sampleToTime(off_t sample);
 	int linesPerTile();