diff --git a/pydocstringformatter/_formatting/formatters_default.py b/pydocstringformatter/_formatting/formatters_default.py
index a3f9d41a..eccc6a4a 100644
--- a/pydocstringformatter/_formatting/formatters_default.py
+++ b/pydocstringformatter/_formatting/formatters_default.py
@@ -152,6 +152,9 @@ def treat_summary(
         description_exists: bool,
     ) -> str:
         """Add a period to the end of single-line docstrings and summaries."""
+        if not summary:
+            return summary
+
         if summary[-1] in self.END_OF_SENTENCE_PUNCTUATION:
             return summary
 
diff --git a/pydocstringformatter/_formatting/formatters_pep257.py b/pydocstringformatter/_formatting/formatters_pep257.py
index 563fab46..34c64c0e 100644
--- a/pydocstringformatter/_formatting/formatters_pep257.py
+++ b/pydocstringformatter/_formatting/formatters_pep257.py
@@ -38,6 +38,9 @@ def treat_summary(
         """Split a summary and body if there is a period after the summary."""
         new_summary = None
 
+        if not summary:
+            return summary
+
         if _utils.is_rst_title(summary):
             return summary
 
diff --git a/tests/data/format/summary_splitter/regression_151.py b/tests/data/format/summary_splitter/regression_151.py
new file mode 100644
index 00000000..f78a2c42
--- /dev/null
+++ b/tests/data/format/summary_splitter/regression_151.py
@@ -0,0 +1,2 @@
+class GithubIssue151:
+    """ """
diff --git a/tests/data/format/summary_splitter/regression_151.py.out b/tests/data/format/summary_splitter/regression_151.py.out
new file mode 100644
index 00000000..7284581c
--- /dev/null
+++ b/tests/data/format/summary_splitter/regression_151.py.out
@@ -0,0 +1,2 @@
+class GithubIssue151:
+    """"""