diff --git a/include/board_design_settings.h b/include/board_design_settings.h
index db08a16cfe..ce3946c9a4 100644
--- a/include/board_design_settings.h
+++ b/include/board_design_settings.h
@@ -298,6 +298,15 @@ public:
         return ( m_viaSizeIndex == 0 && !m_useCustomTrackVia );
     }
 
+    /**
+     * Function UseNetClassDiffPair
+     * returns true if netclass values should be used to obtain appropriate diff pair dimensions.
+     */
+    inline bool UseNetClassDiffPair() const
+    {
+        return ( m_diffPairIndex == 0 && !m_useCustomDiffPair );
+    }
+
     /**
      * Function SetCurrentNetClass
      * Must be called after a netclass selection (or after a netclass parameter change
diff --git a/pcbnew/router/pns_sizes_settings.cpp b/pcbnew/router/pns_sizes_settings.cpp
index 257299ae53..18ead5f729 100644
--- a/pcbnew/router/pns_sizes_settings.cpp
+++ b/pcbnew/router/pns_sizes_settings.cpp
@@ -124,7 +124,13 @@ void SIZES_SETTINGS::Init( BOARD* aBoard, ITEM* aStartItem, int aNet )
         m_viaDrill    = bds.GetCurrentViaDrill();
     }
 
-    if( bds.UseCustomDiffPairDimensions() )
+    if( bds.UseNetClassDiffPair() && netClass != NULL )
+    {
+        m_diffPairWidth  = netClass->GetDiffPairWidth();
+        m_diffPairGap    = netClass->GetDiffPairGap();
+        m_diffPairViaGap = netClass->GetDiffPairViaGap();
+    }
+    else if( bds.UseCustomDiffPairDimensions() )
     {
         m_diffPairWidth  = bds.GetCustomDiffPairWidth();
         m_diffPairGap    = bds.GetCustomDiffPairGap();