diff --git a/CHANGELOG.md b/CHANGELOG.md
index e6d4206a7..3907acab1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -87,6 +87,7 @@ CLI command and its behaviour. There are no guarantees of stability for the
 - Reduced python-debian minimum version to 0.1.34. (#808)
 - Fix issue in `annotate` where `--single-line` and `--multi-line` would not
   correctly raise an error with an incompatible comment style. (#853)
+- Fix parsing existing copyright lines when they do not have a year (#861)
 
 ### Security
 
diff --git a/src/reuse/_util.py b/src/reuse/_util.py
index 676762b76..7a410d5f3 100644
--- a/src/reuse/_util.py
+++ b/src/reuse/_util.py
@@ -295,9 +295,9 @@ def _parse_copyright_year(year: str) -> list:
     """Parse copyright years and return list."""
     if not year:
         ret = []
-    if re.match(r"\d{4}$", year):
+    elif re.match(r"\d{4}$", year):
         ret = [int(year)]
-    if re.match(r"\d{4} ?- ?\d{4}$", year):
+    elif re.match(r"\d{4} ?- ?\d{4}$", year):
         ret = [int(year[:4]), int(year[-4:])]
     return ret
 
@@ -393,7 +393,9 @@ def merge_copyright_lines(copyright_lines: Set[str]) -> Set[str]:
             years += copy["year"]
 
         year: Optional[str] = None
-        if min(years) == max(years):
+        if not years:
+            year = None
+        elif min(years) == max(years):
             year = min(years)
         else:
             year = f"{min(years)} - {max(years)}"