diff --git a/src/cpcformats.c b/src/cpcformats.c
index 840e5aeb..cd89261c 100644
--- a/src/cpcformats.c
+++ b/src/cpcformats.c
@@ -373,7 +373,7 @@ void Save_SGX(T_IO_Context * context)
   int i;
 
   File_error =  1;
-  n_colors = Count_used_colors(color_usage);
+  n_colors = Current_layer_count_used_colors(context, color_usage);
   for (i = 16; i < 256; i++)
   {
     if (color_usage[i] != 0)
diff --git a/src/loadsavefuncs.c b/src/loadsavefuncs.c
index 82dafb7d..6beaf1b0 100644
--- a/src/loadsavefuncs.c
+++ b/src/loadsavefuncs.c
@@ -324,3 +324,27 @@ void Palette_64_to_256(T_Palette palette)
     palette[i].B = (palette[i].B << 2)|(palette[i].B >> 4);
   }
 }
+
+word Current_layer_count_used_colors(T_IO_Context *context, dword *usage)
+{
+  dword nb_colors = 0;
+  int i;
+  word x, y;
+
+  for (i = 0; i < 256; i++) usage[i] = 0;
+
+  for (y = 0; y < context->Height; y++)
+  {
+    for (x = 0; x < context->Width; x++)
+      usage[Get_pixel(context, x, y)]++;
+  }
+
+  // count the total number of unique used colors
+  for (i = 0; i < 256; i++)
+  {
+    if (usage[i] != 0)
+      nb_colors++;
+  }
+
+  return nb_colors;
+}
diff --git a/src/loadsavefuncs.h b/src/loadsavefuncs.h
index e9ec4e50..ee05da0a 100644
--- a/src/loadsavefuncs.h
+++ b/src/loadsavefuncs.h
@@ -45,4 +45,6 @@ FILE * Open_file_write_with_alternate_ext(T_IO_Context *context, const char * ex
 void Palette_256_to_64(T_Palette palette);
 void Palette_64_to_256(T_Palette palette);
 
+word Current_layer_count_used_colors(T_IO_Context *context, dword *usage);
+
 #endif