diff --git a/kdevplatform/sublime/ideallayout.cpp b/kdevplatform/sublime/ideallayout.cpp
--- a/kdevplatform/sublime/ideallayout.cpp
+++ b/kdevplatform/sublime/ideallayout.cpp
@@ -202,9 +202,10 @@
         return x + currentLineWidth + r;
     }
 
-    const bool shrink = rect.height() < sizeHint().height();
+    bool shrink = rect.height() < sizeHint().height();
 
-    const int maximumHeight = rect.height() / _items.size();
+    // space left per button after removing available space for buttonSpacing
+    const int maximumHeight = (rect.height() - buttonSpacing * (_items.size() - 1)) / _items.size();
     int shrinkedHeight = -1;
 
     if (shrink) {
@@ -218,9 +219,13 @@
             return acc;
         });
 
-        Q_ASSERT(_items.size() != smallItemCount); // should be true since rect.width != sizeHint.width
-        // evenly distribute surplus height over large items
-        shrinkedHeight = maximumHeight + surplus / (_items.size() - smallItemCount);
+        if (_items.size() != smallItemCount) {
+            // evenly distribute surplus height over large items
+            shrinkedHeight = maximumHeight + surplus / (_items.size() - smallItemCount);
+        } else {
+            // only small items, no shrinkage needed
+            shrink = false;
+        }
     }
 
     for (QLayoutItem* item : _items) {
@@ -260,9 +265,10 @@
         return y + currentLineHeight + b;
     }
 
-    const bool shrink = rect.width() < sizeHint().width();
+    bool shrink = rect.width() < sizeHint().width();
 
-    const int maximumWidth = rect.width() / _items.size();
+    // space left per button after removing available space for buttonSpacing
+    const int maximumWidth = (rect.width() - buttonSpacing * (_items.size() - 1)) / _items.size();
     int shrinkedWidth = -1;
 
     if (shrink) {
@@ -276,9 +282,12 @@
             return acc;
         });
 
-        Q_ASSERT(_items.size() != smallItemCount); // should be true since rect.width != sizeHint.width
-        // evenly distribute surplus width on the large items
-        shrinkedWidth = maximumWidth + surplus / (_items.size() - smallItemCount);
+        if (_items.size() != smallItemCount) {
+            // evenly distribute surplus width on the large items
+            shrinkedWidth = maximumWidth + surplus / (_items.size() - smallItemCount);
+        } else {
+            shrink = false;
+        }
     }
 
     for (QLayoutItem* item : _items) {