diff --git a/src/gui/image_slice_window.cpp b/src/gui/image_slice_window.cpp
index fe92cfca..cf0806db 100644
--- a/src/gui/image_slice_window.cpp
+++ b/src/gui/image_slice_window.cpp
@@ -23,7 +23,7 @@ ImageSlice::ImageSlice(const Image& source, const wxSize& target_size)
 	, sharpen(true), sharpen_amount(25)
 {}
 
-void ImageSlice::constrain() {
+void ImageSlice::constrain(PreferedProperty prefer) {
 	sharpen_amount = min(100, max(0, sharpen_amount));
 	// minimum size
 	selection.width  = max(1, selection.width);
@@ -40,7 +40,7 @@ void ImageSlice::constrain() {
 	// fix aspect ratio
 	if (aspect_fixed) {
 		int diff = selection.width * target_size.GetHeight() - selection.height * target_size.GetWidth();
-		if (diff > 0) {
+		if ((diff > 0 && prefer != PREFER_WIDTH) || prefer == PREFER_HEIGHT) {
 			// too wide
 			selection.width  -= int(diff / target_size.GetHeight());
 		} else {
@@ -217,11 +217,11 @@ void ImageSliceWindow::onChangeTop(wxCommandEvent&) {
 }
 void ImageSliceWindow::onChangeWidth(wxCommandEvent&) {
 	slice.selection.width = width->GetValue();
-	onUpdateFromControl();
+	onUpdateFromControl(PREFER_WIDTH);
 }
 void ImageSliceWindow::onChangeHeight(wxCommandEvent&) {
 	slice.selection.height = height->GetValue();
-	onUpdateFromControl();
+	onUpdateFromControl(PREFER_HEIGHT);
 }
 
 void ImageSliceWindow::onChangeFixAspect(wxCommandEvent&) {
@@ -239,7 +239,7 @@ void ImageSliceWindow::onChangeZoomX(wxSpinEvent&) {
 	onUpdateFromControl();
 }
 void ImageSliceWindow::onChangeZoomY(wxSpinEvent&) {
-	slice.zoomY(zoom_x->GetValue() / 100.0);
+	slice.zoomY(zoom_y->GetValue() / 100.0);
 	onUpdateFromControl();
 }
 
@@ -261,8 +261,8 @@ void ImageSliceWindow::onSliceChange(wxCommandEvent&) {
 	updateControls();
 }
 
-void ImageSliceWindow::onUpdateFromControl() {
-	slice.constrain();
+void ImageSliceWindow::onUpdateFromControl(PreferedProperty prefer) {
+	slice.constrain(prefer);
 	preview->update();
 	selector->update();
 	updateControls();
diff --git a/src/gui/image_slice_window.hpp b/src/gui/image_slice_window.hpp
index 3625403e..359d5d38 100644
--- a/src/gui/image_slice_window.hpp
+++ b/src/gui/image_slice_window.hpp
@@ -19,6 +19,13 @@ DECLARE_POINTER_TYPE(AlphaMask);
 
 // ----------------------------------------------------------------------------- : ImageSlice
 
+/// Which option is just changed, and therefore more important?
+enum PreferedProperty
+{	PREFER_NONE
+,	PREFER_WIDTH
+,	PREFER_HEIGHT
+};
+
 /// A slice of an image, i.e. a selected rectangle
 class ImageSlice {
   public:
@@ -35,7 +42,7 @@ class ImageSlice {
 	int sharpen_amount;
 	
 	/// Enforce relations between values
-	void constrain();
+	void constrain(PreferedProperty prefer = PREFER_NONE);
 	/// Get the sliced image
 	Image getSlice() const;
 	
@@ -97,7 +104,7 @@ class ImageSliceWindow : public wxDialog {
 	// --------------------------------------------------- : Updating
 	
 	// The manual controls were changed
-	void onUpdateFromControl();
+	void onUpdateFromControl(PreferedProperty prefer = PREFER_NONE);
 	// Update the values in the controls
 	void updateControls();
 };