diff --git a/pcbnew/drc/drc_engine.cpp b/pcbnew/drc/drc_engine.cpp
index b6b087677f..2f01d5753c 100644
--- a/pcbnew/drc/drc_engine.cpp
+++ b/pcbnew/drc/drc_engine.cpp
@@ -776,6 +776,96 @@ bool DRC_ENGINE::QueryWorstConstraint( DRC_CONSTRAINT_TYPE_T aConstraintId,
 }
 
 
+// fixme: move two functions below to pcbcommon?
+static int matchDpSuffix( const wxString& aNetName, wxString& aComplementNet,
+                          wxString& aBaseDpName )
+{
+    int rv = 0;
+
+    if( aNetName.EndsWith( "+" ) )
+    {
+        aComplementNet = "-";
+        rv = 1;
+    }
+    else if( aNetName.EndsWith( "P" ) )
+    {
+        aComplementNet = "N";
+        rv = 1;
+    }
+    else if( aNetName.EndsWith( "-" ) )
+    {
+        aComplementNet = "+";
+        rv = -1;
+    }
+    else if( aNetName.EndsWith( "N" ) )
+    {
+        aComplementNet = "P";
+        rv = -1;
+    }
+    // Match P followed by 2 digits
+    else if( aNetName.Right( 2 ).IsNumber() && aNetName.Right( 3 ).Left( 1 ) == "P" )
+    {
+        aComplementNet = "N" + aNetName.Right( 2 );
+        rv = 1;
+    }
+    // Match P followed by 1 digit
+    else if( aNetName.Right( 1 ).IsNumber() && aNetName.Right( 2 ).Left( 1 ) == "P" )
+    {
+        aComplementNet = "N" + aNetName.Right( 1 );
+        rv = 1;
+    }
+    // Match N followed by 2 digits
+    else if( aNetName.Right( 2 ).IsNumber() && aNetName.Right( 3 ).Left( 1 ) == "N" )
+    {
+        aComplementNet = "P" + aNetName.Right( 2 );
+        rv = -1;
+    }
+    // Match N followed by 1 digit
+    else if( aNetName.Right( 1 ).IsNumber() && aNetName.Right( 2 ).Left( 1 ) == "N" )
+    {
+        aComplementNet = "P" + aNetName.Right( 1 );
+        rv = -1;
+    }
+    if( rv != 0 )
+    {
+        aBaseDpName = aNetName.Left( aNetName.Length() - aComplementNet.Length() );
+        aComplementNet = aBaseDpName + aComplementNet;
+    }
+
+    return rv;
+}
+
+
+int DRC_ENGINE::IsNetADiffPair( BOARD* aBoard, int aNet, int& aNetP, int& aNetN )
+{
+    wxString refName = aBoard->FindNet( aNet )->GetNetname();
+    wxString dummy, coupledNetName;
+
+    if( int polarity = matchDpSuffix( refName, coupledNetName, dummy ) )
+    {
+        NETINFO_ITEM* net = aBoard->FindNet( coupledNetName );
+
+        if( !net )
+            return false;
+
+        if( polarity > 0 )
+        {
+            aNetP = aNet;
+            aNetN = net->GetNet();
+        }
+        else
+        {
+            aNetP = net->GetNet();
+            aNetN = aNet;
+        }
+
+        return true;
+    }
+
+    return false;
+}
+
+
 DRC_TEST_PROVIDER* DRC_ENGINE::GetTestProvider( const wxString& name ) const
 {
     for( auto prov : m_testProviders )
diff --git a/pcbnew/drc/drc_test_provider_diff_pair_coupling.cpp b/pcbnew/drc/drc_test_provider_diff_pair_coupling.cpp
index 24d7dd848b..1a814b4be9 100644
--- a/pcbnew/drc/drc_test_provider_diff_pair_coupling.cpp
+++ b/pcbnew/drc/drc_test_provider_diff_pair_coupling.cpp
@@ -90,95 +90,6 @@ private:
 };
 
 
-// fixme: move two functions below to pcbcommon?
-static int matchDpSuffix( const wxString& aNetName, wxString& aComplementNet,
-                                             wxString& aBaseDpName )
-{
-    int rv = 0;
-
-    if( aNetName.EndsWith( "+" ) )
-    {
-        aComplementNet = "-";
-        rv = 1;
-    }
-    else if( aNetName.EndsWith( "P" ) )
-    {
-        aComplementNet = "N";
-        rv = 1;
-    }
-    else if( aNetName.EndsWith( "-" ) )
-    {
-        aComplementNet = "+";
-        rv = -1;
-    }
-    else if( aNetName.EndsWith( "N" ) )
-    {
-        aComplementNet = "P";
-        rv = -1;
-    }
-    // Match P followed by 2 digits
-    else if( aNetName.Right( 2 ).IsNumber() && aNetName.Right( 3 ).Left( 1 ) == "P" )
-    {
-        aComplementNet = "N" + aNetName.Right( 2 );
-        rv = 1;
-    }
-    // Match P followed by 1 digit
-    else if( aNetName.Right( 1 ).IsNumber() && aNetName.Right( 2 ).Left( 1 ) == "P" )
-    {
-        aComplementNet = "N" + aNetName.Right( 1 );
-        rv = 1;
-    }
-    // Match N followed by 2 digits
-    else if( aNetName.Right( 2 ).IsNumber() && aNetName.Right( 3 ).Left( 1 ) == "N" )
-    {
-        aComplementNet = "P" + aNetName.Right( 2 );
-        rv = -1;
-    }
-    // Match N followed by 1 digit
-    else if( aNetName.Right( 1 ).IsNumber() && aNetName.Right( 2 ).Left( 1 ) == "N" )
-    {
-        aComplementNet = "P" + aNetName.Right( 1 );
-        rv = -1;
-    }
-    if( rv != 0 )
-    {
-        aBaseDpName = aNetName.Left( aNetName.Length() - aComplementNet.Length() );
-        aComplementNet = aBaseDpName + aComplementNet;
-    }
-
-    return rv;
-}
-
-
-int DRC_ENGINE::IsNetADiffPair( BOARD* aBoard, int aNet, int& aNetP, int& aNetN )
-{
-    wxString refName = aBoard->FindNet( aNet )->GetNetname();
-    wxString dummy, coupledNetName;
-
-    if( int polarity = matchDpSuffix( refName, coupledNetName, dummy ) )
-    {
-        NETINFO_ITEM* net = aBoard->FindNet( coupledNetName );
-
-        if( !net )
-            return false;
-
-        if( polarity > 0 )
-        {
-            aNetP = aNet;
-            aNetN = net->GetNet();
-        }
-        else
-        {
-            aNetP = net->GetNet();
-            aNetN = aNet;
-        }
-
-        return true;
-    }
-
-    return false;
-}
-
 static bool commonParallelProjection( SEG p, SEG n, SEG &pClip, SEG& nClip )
 {
     SEG n_proj_p( p.LineProject( n.A ), p.LineProject( n.B ) );