diff --git a/ion/include/ion/keyboard.h b/ion/include/ion/keyboard.h
index f2b8042bd..ba056ffd2 100644
--- a/ion/include/ion/keyboard.h
+++ b/ion/include/ion/keyboard.h
@@ -43,7 +43,9 @@ public:
   }
   operator uint64_t() const { return m_bitField; }
   void setKey(Key k) {
-    m_bitField |= (uint64_t)1 << (uint8_t)k;
+    if (k != Key::None) {
+      m_bitField |= (uint64_t)1 << (uint8_t)k;
+    }
   }
   void clearKey(Key k) {
     m_bitField &= ~((uint64_t)1 << (uint8_t)k);
diff --git a/ion/src/simulator/shared/layout.cpp b/ion/src/simulator/shared/layout.cpp
index 088e5444c..f930015cc 100644
--- a/ion/src/simulator/shared/layout.cpp
+++ b/ion/src/simulator/shared/layout.cpp
@@ -1,4 +1,5 @@
 #include "layout.h"
+#include <limits.h>
 
 namespace Ion {
 namespace Simulator {
@@ -147,16 +148,51 @@ static void getKeyCenter(int validKeyIndex, SDL_Point * point) {
   makeAbsolute(&sKeyCenters[validKeyIndex], point);
 }
 
+#if 0
+/* TODO: once we use std++14, we can make maxHalfDistanceBetweekAdjacentKeys
+ * constexpr and use it to compute the k_closenessThreshold. */
+
+static int maxHalfDistanceBetweekAdjacentKeys() {
+  int maxSquaredDistance = 0;
+  for (int i=0; i<Keyboard::NumberOfValidKeys-1; i++) {
+    int minSquaredDistance = INT_MAX;
+    for (int j=i+1; j<Keyboard::NumberOfValidKeys; j++) {
+      SDL_Point keyICenter;
+      SDL_Point keyJCenter;
+      getKeyCenter(i, &keyICenter);
+      getKeyCenter(j, &keyJCenter);
+      int dx = keyICenter.x - keyJCenter.x;
+      int dy = keyICenter.y - keyJCenter.y;
+      int squaredDistance = dx*dx + dy*dy;
+      if (squaredDistance < minSquaredDistance) {
+        minSquaredDistance = squaredDistance;
+      }
+    }
+    if (minSquaredDistance > maxSquaredDistance) {
+      maxSquaredDistance = minSquaredDistance;
+    }
+  }
+  return maxSquaredDistance/4; // return 843
+}
+#endif
+
 Keyboard::Key keyAt(SDL_Point * p) {
-  int minSquaredDistance = -1;
+  int minSquaredDistance = INT_MAX;
   Keyboard::Key nearestKey = Keyboard::Key::None;
+  /* The maximal distance between two adjacent keys is between keys Home and
+   * OK (index 3 and 7). So we set the threshold to correspond to slightly over
+   * half the distance between these keys.
+   * TODO: Looking for the maximal distance between adjacent keys could be done
+   * constexpr once we use c++14 standard.
+   * (Cf maxHalfDistanceBetweekAdjacentKeys above) */
+  constexpr int k_closenessThreshold = 3*843/2; // 3*maxHalfDistanceBetweekAdjacentKeys()/2
   for (int i=0; i<Keyboard::NumberOfValidKeys; i++) {
     SDL_Point keyCenter;
     getKeyCenter(i, &keyCenter);
     int dx = keyCenter.x - p->x;
     int dy = keyCenter.y - p->y;
     int squaredDistance = dx*dx + dy*dy;
-    if (squaredDistance < minSquaredDistance || minSquaredDistance < 0) {
+    if (squaredDistance < k_closenessThreshold && squaredDistance < minSquaredDistance) {
       minSquaredDistance = squaredDistance;
       nearestKey = Keyboard::ValidKeys[i];
     }