diff --git a/src/QGCComboBox.h b/src/QGCComboBox.h
index 43f2b415bc554e1d25bf6751a0f92ed5f2ef6745..9949ba41a96a8ef3079022f14b91675c122722ad 100644
--- a/src/QGCComboBox.h
+++ b/src/QGCComboBox.h
@@ -23,7 +23,7 @@ class QGCComboBox : public QComboBox {
     Q_OBJECT
     
 public:
-    QGCComboBox(QWidget* parent = NULL);
+    QGCComboBox(QWidget* parent = nullptr);
     
 	/// @brief Sets the current index on the combo. Signals activated, as well as currentIndexChanged.
 	void simulateUserSetCurrentIndex(int index);
diff --git a/src/QGCFileDownload.h b/src/QGCFileDownload.h
index 4b14f8717906e19d02e24a652fe2dbcacb0f5f39..a4a637fd78ac2c79985200da874e87673d2bd4d2 100644
--- a/src/QGCFileDownload.h
+++ b/src/QGCFileDownload.h
@@ -18,7 +18,7 @@ class QGCFileDownload : public QNetworkAccessManager
     Q_OBJECT
     
 public:
-    QGCFileDownload(QObject* parent = NULL);
+    QGCFileDownload(QObject* parent = nullptr);
     
     /// Download the specified remote file.
     ///     @param remoteFile File to download. Can be http address or file system path.
diff --git a/src/QGCLoggingCategory.cc b/src/QGCLoggingCategory.cc
index c39126f02145bea0749cc6e7bef9f01246014631..15b8c7f329f3b1b703ea566dba4c29399391d79e 100644
--- a/src/QGCLoggingCategory.cc
+++ b/src/QGCLoggingCategory.cc
@@ -25,7 +25,7 @@ QGC_LOGGING_CATEGORY(GeotaggingLog,                 "GeotaggingLog")
 QGC_LOGGING_CATEGORY(RTKGPSLog,                     "RTKGPSLog")
 QGC_LOGGING_CATEGORY(GuidedActionsControllerLog,    "GuidedActionsControllerLog")
 
-QGCLoggingCategoryRegister* _instance = NULL;
+QGCLoggingCategoryRegister* _instance = nullptr;
 const char* QGCLoggingCategoryRegister::_filterRulesSettingsGroup = "LoggingFilters";
 
 QGCLoggingCategoryRegister* QGCLoggingCategoryRegister::instance(void)
diff --git a/src/QGCMapPalette.h b/src/QGCMapPalette.h
index 7896c6746ab879fe1920b083e91e2ea15a3f6a6e..25a1bd90f59514895df06004e4650094ab87e936 100644
--- a/src/QGCMapPalette.h
+++ b/src/QGCMapPalette.h
@@ -47,7 +47,7 @@ class QGCMapPalette : public QObject
     Q_PROPERTY(QColor thumbJoystick READ thumbJoystick NOTIFY paletteChanged)
 
 public:    
-    QGCMapPalette(QObject* parent = NULL);
+    QGCMapPalette(QObject* parent = nullptr);
     
     /// Text color
     QColor text(void)           const { return _text[_lightColors ? 0 : 1]; }
diff --git a/src/QGCQGeoCoordinate.h b/src/QGCQGeoCoordinate.h
index f02f26d1797400459b417c59e2b13f3d6393a2e1..1e9bc3aadc137a2413fa9c29f02106df8db33ebb 100644
--- a/src/QGCQGeoCoordinate.h
+++ b/src/QGCQGeoCoordinate.h
@@ -18,7 +18,7 @@ class QGCQGeoCoordinate : public QObject
     Q_OBJECT
 
 public:
-    QGCQGeoCoordinate(const QGeoCoordinate& coord, QObject* parent = NULL);
+    QGCQGeoCoordinate(const QGeoCoordinate& coord, QObject* parent = nullptr);
 
     Q_PROPERTY(QGeoCoordinate   coordinate  READ coordinate WRITE setCoordinate NOTIFY coordinateChanged)
     Q_PROPERTY(bool             dirty       READ dirty      WRITE setDirty      NOTIFY dirtyChanged)
diff --git a/src/QGCTemporaryFile.h b/src/QGCTemporaryFile.h
index 670e824e64352647514f8d28e2ed1a135aa20112..c46b6bbcc3df630c2b233343de1f596958f59bd6 100644
--- a/src/QGCTemporaryFile.h
+++ b/src/QGCTemporaryFile.h
@@ -28,7 +28,7 @@ public:
 	//			QStandardPaths::TempLocation directory.
 	//		@param template Template for file name following QTemporaryFile rules. Template should NOT include
 	//							directory path, only file name.
-    QGCTemporaryFile(const QString& fileTemplate, QObject* parent = NULL);
+    QGCTemporaryFile(const QString& fileTemplate, QObject* parent = nullptr);
 
 	/// @brief Opens the file in ReadWrite mode.
 	///		@returns false - open failed
diff --git a/src/TerrainTile.cc b/src/TerrainTile.cc
index 55f485a23695becdeaaf987c534c9504a71ad8d4..1b2af80f9af536535d707f0555715284b77e2c56 100644
--- a/src/TerrainTile.cc
+++ b/src/TerrainTile.cc
@@ -24,7 +24,7 @@ TerrainTile::TerrainTile()
     : _minElevation(-1.0)
     , _maxElevation(-1.0)
     , _avgElevation(-1.0)
-    , _data(NULL)
+    , _data(nullptr)
     , _gridSizeLat(-1)
     , _gridSizeLon(-1)
     , _isValid(false)
@@ -39,7 +39,7 @@ TerrainTile::~TerrainTile()
             delete _data[i];
         }
         delete _data;
-        _data = NULL;
+        _data = nullptr;
     }
 }
 
@@ -48,7 +48,7 @@ TerrainTile::TerrainTile(QByteArray byteArray)
     : _minElevation(-1.0)
     , _maxElevation(-1.0)
     , _avgElevation(-1.0)
-    , _data(NULL)
+    , _data(nullptr)
     , _gridSizeLat(-1)
     , _gridSizeLon(-1)
     , _isValid(false)