diff --git a/modules/graphics/src/main/native-glass/gtk/GlassApplication.cpp b/modules/graphics/src/main/native-glass/gtk/GlassApplication.cpp
index c909e70..4de37d6 100644
--- a/modules/graphics/src/main/native-glass/gtk/GlassApplication.cpp
+++ b/modules/graphics/src/main/native-glass/gtk/GlassApplication.cpp
@@ -271,7 +271,7 @@ JNIEXPORT jlong JNICALL Java_com_sun_glass_ui_gtk_GtkApplication_staticView_1get
 
     static gint multi_click_time = -1;
     if (multi_click_time == -1) {
-        g_object_get(gtk_settings_get_default(), "gtk-double-click-time", &multi_click_time, NULL);
+        g_object_get(gtk_settings_get_default(), "gtk-double-click-time", &multi_click_time, (char*)NULL);
     }
     return (jlong)multi_click_time;
 }
@@ -290,7 +290,7 @@ JNIEXPORT jint JNICALL Java_com_sun_glass_ui_gtk_GtkApplication_staticView_1getM
     static gint multi_click_dist = -1;
 
     if (multi_click_dist == -1) {
-        g_object_get(gtk_settings_get_default(), "gtk-double-click-distance", &multi_click_dist, NULL);
+        g_object_get(gtk_settings_get_default(), "gtk-double-click-distance", &multi_click_dist, (char*)NULL);
     }
     return multi_click_dist;
 }
diff --git a/modules/graphics/src/main/native-glass/gtk/GlassCommonDialogs.cpp b/modules/graphics/src/main/native-glass/gtk/GlassCommonDialogs.cpp
index c53929d..5941b2c 100644
--- a/modules/graphics/src/main/native-glass/gtk/GlassCommonDialogs.cpp
+++ b/modules/graphics/src/main/native-glass/gtk/GlassCommonDialogs.cpp
@@ -118,7 +118,7 @@ JNIEXPORT jobject JNICALL Java_com_sun_glass_ui_gtk_GtkCommonDialogs__1showFileC
             GTK_RESPONSE_CANCEL,
             (chooser_type == GTK_FILE_CHOOSER_ACTION_OPEN ? GTK_STOCK_OPEN : GTK_STOCK_SAVE),
             GTK_RESPONSE_ACCEPT,
-            NULL);
+            (char*)NULL);
 
     if (chooser_type == GTK_FILE_CHOOSER_ACTION_SAVE) {
         gtk_file_chooser_set_current_name(GTK_FILE_CHOOSER(chooser), chooser_filename);
@@ -205,7 +205,7 @@ JNIEXPORT jstring JNICALL Java_com_sun_glass_ui_gtk_GtkCommonDialogs__1showFolde
             GTK_RESPONSE_CANCEL,
             GTK_STOCK_OPEN,
             GTK_RESPONSE_ACCEPT,
-            NULL);
+            (char*)NULL);
 
     if (chooser_folder != NULL) {
         gtk_file_chooser_set_current_folder(GTK_FILE_CHOOSER(chooser),
diff --git a/modules/graphics/src/main/native-glass/gtk/glass_dnd.cpp b/modules/graphics/src/main/native-glass/gtk/glass_dnd.cpp
index f85b1da..d523809 100644
--- a/modules/graphics/src/main/native-glass/gtk/glass_dnd.cpp
+++ b/modules/graphics/src/main/native-glass/gtk/glass_dnd.cpp
@@ -688,7 +688,7 @@ static gboolean dnd_source_set_image(GdkWindow *requestor, GdkAtom property, Gdk
     mainEnv->CallVoidMethod(pixels, jPixelsAttachData, PTR_TO_JLONG(&pixbuf));
 
     if (!EXCEPTION_OCCURED(mainEnv)
-            && gdk_pixbuf_save_to_buffer(pixbuf, &buffer, &size, type, NULL, NULL)) {
+            && gdk_pixbuf_save_to_buffer(pixbuf, &buffer, &size, type, NULL, (char*)NULL)) {
         gdk_property_change(requestor, property, target,
                 8, GDK_PROP_MODE_REPLACE, (guchar *)buffer, size);
         result = TRUE;
diff --git a/modules/graphics/src/main/native-glass/gtk/glass_window_ime.cpp b/modules/graphics/src/main/native-glass/gtk/glass_window_ime.cpp
index 82e54d1..49ba05e 100644
--- a/modules/graphics/src/main/native-glass/gtk/glass_window_ime.cpp
+++ b/modules/graphics/src/main/native-glass/gtk/glass_window_ime.cpp
@@ -204,7 +204,7 @@ static XIMStyle get_best_supported_style(XIM im_xim)
     int i;
     XIMStyle result = 0;
 
-    if (XGetIMValues(im_xim, XNQueryInputStyle, &styles, NULL) != NULL) { // NULL means it's OK
+    if (XGetIMValues(im_xim, XNQueryInputStyle, &styles, (char*)NULL) != NULL) { // NULL means it's OK
         return 0;
     }
 
@@ -244,13 +244,13 @@ void WindowContextBase::enableOrResetIME() {
                 XNPreeditDoneCallback, &doneCallback,
                 XNPreeditDrawCallback, &drawCallback,
                 XNPreeditCaretCallback, &caretCallback,
-                NULL);
+                (char*)NULL);
 
         xim.ic = XCreateIC(xim.im,
                 XNInputStyle, styles,
                 XNClientWindow, GDK_WINDOW_XID(gdk_window),
                 XNPreeditAttributes, list,
-                NULL);
+                (char*)NULL);
 
         XFree(list);