diff --git a/testing/btest/Baseline/bifs.sub_bytes/.stderr b/testing/btest/Baseline/bifs.sub_bytes/.stderr
new file mode 100644
index 0000000000..49d861c74c
--- /dev/null
+++ b/testing/btest/Baseline/bifs.sub_bytes/.stderr
@@ -0,0 +1 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
diff --git a/testing/btest/Baseline/bifs.sub_bytes/out b/testing/btest/Baseline/bifs.sub_bytes/out
new file mode 100644
index 0000000000..6d1b207b13
--- /dev/null
+++ b/testing/btest/Baseline/bifs.sub_bytes/out
@@ -0,0 +1,9 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+bcde
+bcde
+bcde
+bcde
+bcde
+bcde
+bcde
+bcde
diff --git a/testing/btest/bifs/sub_bytes.zeek b/testing/btest/bifs/sub_bytes.zeek
new file mode 100644
index 0000000000..a1aa7217db
--- /dev/null
+++ b/testing/btest/bifs/sub_bytes.zeek
@@ -0,0 +1,22 @@
+# @TEST-DOC: Test the sub_bytes() function.
+#
+# @TEST-EXEC: zeek -b %INPUT >out
+# @TEST-EXEC: btest-diff out
+# @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff .stderr
+
+# These tests are to ensure that script optimization gets all the permutations
+# correct, for varying combinations of constant and variable arguments.
+
+global s = "abcdefghij";
+global a = 2;
+global b = 4;
+
+print sub_bytes(s, a, b);
+print sub_bytes(s, 2, b);
+print sub_bytes(s, a, 4);
+print sub_bytes(s, 2, 4);
+
+print sub_bytes("abcdefghij", a, b);
+print sub_bytes("abcdefghij", 2, b);
+print sub_bytes("abcdefghij", a, 4);
+print sub_bytes("abcdefghij", 2, 4);