diff --git a/src/etc/unicode.py b/src/etc/unicode.py
index 864cf3daee07e..afb3d16848085 100755
--- a/src/etc/unicode.py
+++ b/src/etc/unicode.py
@@ -235,6 +235,10 @@ def emit_decomp_module(f, canon, compat):
 rf = open(r, "w")
 
 (canon_decomp, compat_decomp, gencats) = load_unicode_data("UnicodeData.txt")
+
+# Explain that the source code was generated by this script.
+rf.write('// The following code was generated by "src/etc/unicode.py"\n\n')
+
 emit_property_module(rf, "general_category", gencats)
 
 #emit_decomp_module(rf, canon_decomp, compat_decomp)
diff --git a/src/libcore/unicode.rs b/src/libcore/unicode.rs
index a13d66c48ee0c..34175f9888ffa 100644
--- a/src/libcore/unicode.rs
+++ b/src/libcore/unicode.rs
@@ -10,6 +10,8 @@
 
 #[doc(hidden)]; // FIXME #3538
 
+// The following code was generated by "src/etc/unicode.py"
+
 pub mod general_category {
 
     fn bsearch_range_table(c: char, r: &'static [(char,char)]) -> bool {