diff --git a/tests/copyright_check_untracked_test.py b/tests/copyright_check_untracked_test.py
index cbe0fd5c6..3b1888ce4 100755
--- a/tests/copyright_check_untracked_test.py
+++ b/tests/copyright_check_untracked_test.py
@@ -165,5 +165,44 @@ def git(repo, *args):
     check(rc.returncode != 0, "the same generated source TRACKED is still an error: it is repo content now",
           rc.stdout + rc.stderr)
 
+# --fix must not delete blank lines (#2183 review). The licence block's own blank comment lines reduce to the empty
+# string, and canonical_notice_line() treated "" as a notice line. So add_notice() deleted every blank or bare `//`
+# line in the header window: on #2183's 13 two-liner headers --fix gave +143 -68, dropping the separator after the
+# description, the blank lines between #include groups and the one after `namespace {`. And repair_notice()'s
+# doubled-block dedupe dropped every blank line after the first in the WHOLE file. Both cases compare the written
+# file with the exact expected text, so a single lost line fails them.
+CPP_NOTICE = "".join(("//" + line[1:]) for line in NOTICE.splitlines(keepends=True))
+CPP_BODY = ("//\n// x.cpp -- what this file is for.\n//\n// A second paragraph.\n\n"
+            "#include <cstdio>\n#include <string>\n\n#include \"x.h\"\n\nnamespace {\n\nint g = 0;\n\n}  // namespace\n")
+with tempfile.TemporaryDirectory() as repo:
+    git(repo, "init", "-q")
+    path = os.path.join(repo, "twoliner.cpp")
+    with open(path, "w") as f:
+        f.write("// Copyright 2026 bong-water-water-bong\n// SPDX-License-Identifier: Apache-2.0\n" + CPP_BODY)
+    run(repo, "--fix")
+    with open(path) as f:
+        fixed = f.read()
+    check(fixed == CPP_NOTICE + CPP_BODY,
+          "--fix on a two-liner header keeps every blank and bare `//` line below it",
+          "lost %d blank line(s)" % (CPP_BODY.count("\n\n") - fixed.count("\n\n")))
+    rc = run(repo, "--check")
+    check(rc.returncode == 0, "...and the file it wrote passes --check", rc.stdout + rc.stderr)
+
+with tempfile.TemporaryDirectory() as repo:
+    git(repo, "init", "-q")
+    path = os.path.join(repo, "nearmiss.cpp")
+    # blank lines well past the 20-line header window: the repair path reads the whole file
+    long_body = CPP_BODY + "".join("int v%d = %d;\n" % (i, i) for i in range(30)) + "\nint z;\n\nint w;\n"
+    with open(path, "w") as f:
+        f.write(CPP_NOTICE + "// Copyright 2026 bong-water-bong\n// SPDX-License-Identifier: Apache-2.0\n" + long_body)
+    run(repo, "--fix")
+    with open(path) as f:
+        fixed = f.read()
+    check(fixed == CPP_NOTICE + long_body,
+          "--fix repairing a near-miss holder keeps every blank line in the file, past the header window too",
+          "lost %d blank line(s)" % (long_body.count("\n\n") - fixed[len(CPP_NOTICE):].count("\n\n")))
+    rc = run(repo, "--check")
+    check(rc.returncode == 0, "...and the repaired file passes --check", rc.stdout + rc.stderr)
+
 print(f"copyright_check_untracked_test: {len(FAIL)} failure(s)")
 sys.exit(1 if FAIL else 0)
diff --git a/tools/copyright.py b/tools/copyright.py
index 2e3888f6a..6af956bba 100755
--- a/tools/copyright.py
+++ b/tools/copyright.py
@@ -229,7 +229,12 @@ def near_miss_holder(line):
     return n >= HOLDER_NEAR_MISS_PREFIX
 
 
-_CANON_LINES = {re.sub(r"^\W+", "", n).strip() for n in NOTICE}
+# The licence block's own blank comment lines (`#`, `//`) reduce to "", so a set built from every NOTICE line held the
+# empty string, and canonical_notice_line() said yes to every blank or bare-comment line in a file. add_notice() then
+# deleted each one in the header window (the separator after the description, the blank lines between #include groups
+# and after `namespace {`), and repair_notice()'s doubled-block dedupe deleted every blank line after the first in the
+# whole file. Only lines with words in them can be a claim, so only those are canonical.
+_CANON_LINES = {k for k in (re.sub(r"^\W+", "", n).strip() for n in NOTICE) if k}
 
 
 def canonical_notice_line(line):
@@ -241,7 +246,8 @@ def canonical_notice_line(line):
     cover it by construction: it returns False for an exact holder, because an exact holder next to the canonical block
     is the *repaired* state. The block already contains both lines, so a copy inside the window is not a second claim.
     """
-    return re.sub(r"^\W+", "", line).strip() in _CANON_LINES
+    key = re.sub(r"^\W+", "", line).strip()
+    return bool(key) and key in _CANON_LINES
 
 
 def repair_notice(text, block):