diff --git a/ion/src/simulator/keyboard/fltkkbd.cpp b/ion/src/simulator/keyboard/fltkkbd.cpp
index 16a82857b..a9cf4d81e 100644
--- a/ion/src/simulator/keyboard/fltkkbd.cpp
+++ b/ion/src/simulator/keyboard/fltkkbd.cpp
@@ -1,8 +1,15 @@
+#include <assert.h>
 #include "fltkkbd.h"
 
+#define KEYBOARD_ROWS 7
+#define KEYBOARD_COLUMNS 5
+
 FltkKbd::FltkKbd(int x, int y, int w, int h) : Fl_Group(x, y, w, h) {
+  assert(KEYBOARD_ROWS*KEYBOARD_COLUMNS == ION_NUMBER_OF_KEYS);
+  int key_width = w/KEYBOARD_COLUMNS;
+  int key_height = h/KEYBOARD_ROWS;
   for (int k=0; k<ION_NUMBER_OF_KEYS; k++) {
-    m_buttons[k] = new Fl_Button(x+(k*w)/ION_NUMBER_OF_KEYS, y, w/ION_NUMBER_OF_KEYS, h);
+    m_buttons[k] = new Fl_Button(x + (k%KEYBOARD_COLUMNS)*key_width, y + (k/KEYBOARD_COLUMNS)*key_height, key_width, key_height);
   }
   end();
 }