diff --git a/requirements.txt b/requirements.txt
index 18fd2d0aa..d848c07c0 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,3 +1,7 @@
+# The order of packages is significant, because pip processes them in the order
+# of appearance. Changing the order has an impact on the overall integration
+# process, which may cause wedges in the gate later.
+
 pbr>=0.6,!=0.7,<1.0
 
 argparse
diff --git a/test-requirements.txt b/test-requirements.txt
index da16dae09..0db4b0a3c 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -1,3 +1,7 @@
+# The order of packages is significant, because pip processes them in the order
+# of appearance. Changing the order has an impact on the overall integration
+# process, which may cause wedges in the gate later.
+
 hacking>=0.8.0,<0.9
 
 coverage>=3.6