diff --git a/src/tools/gif2c.rb b/src/tools/gif2c.rb
index e30f119..7f5677a 100755
--- a/src/tools/gif2c.rb
+++ b/src/tools/gif2c.rb
@@ -70,9 +70,14 @@ if times.uniq.count==1
 	times = times[0, 1]
 end
 
+total_x, total_y = frames.first.columns, frames.first.rows
+
 STDERR.print "Getting colors..."
 colors = []
 frames.each do |frame|
+	if frame.columns!=total_x || frame.rows!=total_y
+		raise "The gif file has frames with different sizes. Such gifs are not supported at the moment, sorry."
+	end
 	frame.columns.times do |x|
 		frame.rows.times do |y|
 			color = frame.pixel_color(x, y).to_color(Magick::AllCompliance, true, 8, true)[1,8].to_i(16)