diff --git a/Rakefile b/Rakefile
index b3be1a2..8a056c8 100644
--- a/Rakefile
+++ b/Rakefile
@@ -143,7 +143,7 @@ task :doc => ["Doxyfile", "README.md"] do |t|
 end
 
 desc "compile source into object"
-rule '.o' => ['.c', "#{LIBOPENCM3_LIB}/lib#{STM32F1_LIB}.a"] do |t|
+rule '.o' => ['.c', '.h', "#{LIBOPENCM3_LIB}/lib#{STM32F1_LIB}.a"] do |t|
   sh "#{CC} #{cflags} #{archflags} -o #{t.name} -c #{t.prerequisites[0]}"
 end