diff --git a/vncviewer/OSXPixelBuffer.cxx b/vncviewer/OSXPixelBuffer.cxx
index a3ee9d0..e9100f2 100644
--- a/vncviewer/OSXPixelBuffer.cxx
+++ b/vncviewer/OSXPixelBuffer.cxx
@@ -20,8 +20,6 @@
 #include <config.h>
 #endif
 
-#include <assert.h>
-
 #include <ApplicationServices/ApplicationServices.h>
 
 #include <FL/Fl_Window.H>
@@ -50,13 +48,14 @@
     throw rfb::Exception(_("Not enough memory for framebuffer"));
 
   lut = CGColorSpaceCreateDeviceRGB();
-  assert(lut);
+  if (!lut)
+    throw rfb::Exception(_("Could not create framebuffer device"));
 
   bitmap = CGBitmapContextCreate(data, width, height, 8, width*4, lut,
                                  kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Little);
-  assert(bitmap);
-
   CGColorSpaceRelease(lut);
+  if (!bitmap)
+    throw rfb::Exception(_("Could not create framebuffer bitmap"));
 }
 
 
diff --git a/vncviewer/Viewport.cxx b/vncviewer/Viewport.cxx
index 66a7841..4daff16 100644
--- a/vncviewer/Viewport.cxx
+++ b/vncviewer/Viewport.cxx
@@ -27,6 +27,7 @@
 
 #include <rfb/CMsgWriter.h>
 #include <rfb/LogWriter.h>
+#include <rfb/Exception.h>
 
 // FLTK can pull in the X11 headers on some systems
 #ifndef XK_VoidSymbol
@@ -452,6 +453,8 @@
     fb = new X11PixelBuffer(w, h);
 #endif
   } catch (rdr::Exception& e) {
+    vlog.error(_("Unable to create platform specific framebuffer: %s"), e.str());
+    vlog.error(_("Using platform independent framebuffer"));
     fb = new FLTKPixelBuffer(w, h);
   }
 
diff --git a/vncviewer/X11PixelBuffer.cxx b/vncviewer/X11PixelBuffer.cxx
index d84357c..59b90e2 100644
--- a/vncviewer/X11PixelBuffer.cxx
+++ b/vncviewer/X11PixelBuffer.cxx
@@ -21,7 +21,6 @@
 #include <config.h>
 #endif
 
-#include <assert.h>
 #include <stdlib.h>
 
 #include <FL/x.H>
@@ -104,10 +103,12 @@
   if (!setupShm()) {
     xim = XCreateImage(fl_display, fl_visual->visual, fl_visual->depth,
                        ZPixmap, 0, 0, width, height, BitmapPad(fl_display), 0);
-    assert(xim);
+    if (!xim)
+      throw rfb::Exception(_("Could not create framebuffer image"));
 
     xim->data = (char*)malloc(xim->bytes_per_line * xim->height);
-    assert(xim->data);
+    if (!xim->data)
+      throw rfb::Exception(_("Not enough memory for framebuffer"));
   }
 
   data = (rdr::U8*)xim->data;