diff --git a/exercise3-2/build.sh b/exercise3-2/build.sh
index 9127896..97d0fe2 100755
--- a/exercise3-2/build.sh
+++ b/exercise3-2/build.sh
@@ -1,4 +1,7 @@
 #!/bin/bash
 
-tar xzf /opt/exercise3-2-build-output.tar.gz
+if [ ! -d build ]; then
+  tar xzf /opt/exercise3-2-build-output.tar.gz
+fi
+
 colcon build