diff --git a/m4/.gitignore b/m4/.gitignore
new file mode 100644
index 0000000..f76d481
--- /dev/null
+++ b/m4/.gitignore
@@ -0,0 +1,3 @@
+# This directory is used by autotools, so we ignore all files except this one.
+*
+!.gitignore