diff --git a/Rakefile b/Rakefile
index 9754420..ba9ff3d 100644
--- a/Rakefile
+++ b/Rakefile
@@ -28,6 +28,11 @@ end
 LIBOPENCM3_DIR = "libopencm3"
 LIBOPENCM3_INC = LIBOPENCM3_DIR+"/include"
 LIBOPENCM3_LIBS = LIBOPENCM3_DIR+"/lib"
+# get libopencm3
+unless File.file?("./#{LIBOPENCM3_DIR}/scripts/genlink.py") then
+  sh "git submodule init"
+  sh "git submodule update"
+end
 LIBOPENCM3_LIB = "opencm3_" + `./#{LIBOPENCM3_DIR}/scripts/genlink.py #{LIBOPENCM3_DIR}/ld/devices.data #{DEVICE} FAMILY`
 
 # source code used by the firmware
@@ -137,14 +142,8 @@ def dependencies(source, done=[])
   return done
 end
 
-desc "get libopencm3"
-file LIBOPENCM3_DIR+"/Makefile" do
-  sh "git submodule init"
-  sh "git submodule update"
-end
-
 desc "compile libopencm3"
-file "#{LIBOPENCM3_LIBS}/lib#{LIBOPENCM3_LIB}.a" => LIBOPENCM3_DIR+"/Makefile" do
+file "#{LIBOPENCM3_LIBS}/lib#{LIBOPENCM3_LIB}.a" do
   sh "make --directory #{LIBOPENCM3_DIR}"
 end