diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..33c3d77
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1,5 @@
+# Certificate files must never be line-ending converted (CRLF would corrupt
+# trust-store parsing on Linux CI runners / Docker builds).
+*.crt -text
+*.pem -text
+*.cer -text