diff --git a/m4/.gitignore b/m4/.gitignore
index c44e4c29..bb91e508 100644
--- a/m4/.gitignore
+++ b/m4/.gitignore
@@ -1,4 +1,5 @@
 # Ignore libtoolize-generated files.
 *.m4
 !as_case.m4
+!ax_pthread.m4
 !libuv-check-flags.m4