diff --git a/common/gal/cairo/cairo_gal.cpp b/common/gal/cairo/cairo_gal.cpp
index e8e1523f03..6a5d56e6a0 100644
--- a/common/gal/cairo/cairo_gal.cpp
+++ b/common/gal/cairo/cairo_gal.cpp
@@ -1251,6 +1251,7 @@ CAIRO_GAL::CAIRO_GAL( GAL_DISPLAY_OPTIONS& aDisplayOptions, wxWindow* aParent,
     m_mainBuffer = 0;
     m_overlayBuffer = 0;
     m_tempBuffer = 0;
+    m_savedBuffer = 0;
     m_validCompositor = false;
     SetTarget( TARGET_NONCACHED );
 
@@ -1324,7 +1325,6 @@ void CAIRO_GAL::endDrawing()
 
     // Now translate the raw context data from the format stored
     // by cairo into a format understood by wxImage.
-
     pixman_image_t* dstImg = pixman_image_create_bits(
             wxPlatformInfo::Get().GetEndianness() == wxENDIAN_LITTLE ? PIXMAN_b8g8r8
                                                                      : PIXMAN_r8g8b8,
@@ -1644,7 +1644,6 @@ void CAIRO_GAL_BASE::DrawGrid()
     int gridEndY = KiROUND( ( worldEndPoint.y - m_gridOrigin.y ) / gridScreenSize.y );
 
     // Ensure start coordinate > end coordinate
-
     SWAP( gridStartX, >, gridEndX );
     SWAP( gridStartY, >, gridEndY );
 
@@ -1691,6 +1690,7 @@ void CAIRO_GAL_BASE::DrawGrid()
     {
         m_lineWidthIsOdd = true;
         m_isStrokeEnabled = true;
+
         for( int j = gridStartY; j <= gridEndY; j++ )
         {
             bool tickY = ( j % m_gridTick == 0 );
diff --git a/pcbnew/drc/drc_test_provider_copper_clearance.cpp b/pcbnew/drc/drc_test_provider_copper_clearance.cpp
index 57c1b9a326..4feb7b2c55 100644
--- a/pcbnew/drc/drc_test_provider_copper_clearance.cpp
+++ b/pcbnew/drc/drc_test_provider_copper_clearance.cpp
@@ -435,9 +435,9 @@ void DRC_TEST_PROVIDER_COPPER_CLEARANCE::testItemAgainstZones( BOARD_ITEM* aItem
                     }
                 }
 
-                if( zoneTree->QueryColliding( itemBBox, itemShape.get(), aLayer,
-                                              std::max( 0, clearance - m_drcEpsilon ),
-                                              &actual, &pos ) )
+                if( zoneTree && zoneTree->QueryColliding( itemBBox, itemShape.get(), aLayer,
+                                                          std::max( 0, clearance - m_drcEpsilon ),
+                                                          &actual, &pos ) )
                 {
                     std::shared_ptr<DRC_ITEM> drce = DRC_ITEM::Create( DRCE_CLEARANCE );
 
@@ -480,9 +480,9 @@ void DRC_TEST_PROVIDER_COPPER_CLEARANCE::testItemAgainstZones( BOARD_ITEM* aItem
                                                          aLayer );
                     clearance = constraint.GetValue().Min();
 
-                    if( zoneTree->QueryColliding( itemBBox, holeShape.get(), aLayer,
-                                                  std::max( 0, clearance - m_drcEpsilon ),
-                                                  &actual, &pos ) )
+                    if( zoneTree && zoneTree->QueryColliding( itemBBox, holeShape.get(), aLayer,
+                                                              std::max( 0, clearance - m_drcEpsilon ),
+                                                              &actual, &pos ) )
                     {
                         std::shared_ptr<DRC_ITEM> drce = DRC_ITEM::Create( DRCE_HOLE_CLEARANCE );
 
@@ -740,8 +740,8 @@ bool DRC_TEST_PROVIDER_COPPER_CLEARANCE::testPadAgainstItem( PAD* pad, SHAPE* pa
         otherShape.reset( new SHAPE_SEGMENT( pos, pos, otherVia->GetDrill() ) );
 
         if( clearance > 0 && padShape->Collide( otherShape.get(),
-                                                 std::max( 0, clearance - m_drcEpsilon ),
-                                                 &actual, &pos ) )
+                                                std::max( 0, clearance - m_drcEpsilon ),
+                                                &actual, &pos ) )
         {
             std::shared_ptr<DRC_ITEM> drce = DRC_ITEM::Create( DRCE_HOLE_CLEARANCE );
 
@@ -874,7 +874,8 @@ void DRC_TEST_PROVIDER_COPPER_CLEARANCE::testZonesToZones()
                     continue;
 
                 // Test for same net
-                if( zoneRef->GetNetCode() == zoneToTest->GetNetCode() && zoneRef->GetNetCode() >= 0 )
+                if( zoneRef->GetNetCode() == zoneToTest->GetNetCode()
+                  && zoneRef->GetNetCode() >= 0 )
                     continue;
 
                 // test for different priorities
diff --git a/pcbnew/pcb_painter.cpp b/pcbnew/pcb_painter.cpp
index 8b363e090f..ce1075e45e 100644
--- a/pcbnew/pcb_painter.cpp
+++ b/pcbnew/pcb_painter.cpp
@@ -995,7 +995,7 @@ void PCB_PAINTER::draw( const PAD* aPad, int aLayer )
                 textpos.y = -textpos.y;
 
                 // approximate the size of the pad number text:
-                double tsize = 1.5 * padsize.x / PrintableCharCount( padNumber );
+                double tsize = 1.5 * padsize.x / std::max( PrintableCharCount( padNumber ), 1 );
                 tsize = std::min( tsize, size );
 
                 // Use a smaller text size to handle interline, pen size...