diff --git a/lib/include/edapi/error.h b/lib/include/edapi/error.h
index b235020..afb7514 100644
--- a/lib/include/edapi/error.h
+++ b/lib/include/edapi/error.h
@@ -22,4 +22,9 @@ typedef enum {
  */
 #define goto_if_error(r, l) do { if (ED_ERROR(r)) goto l; } while(0)
 
+/**
+ * Return `r` if `b` is true.
+ */
+#define return_if_true(b, r) do { if (b) return r; } while(0)
+
 #endif
diff --git a/lib/src/journal/file.c b/lib/src/journal/file.c
index 9438de9..ff8e1f2 100644
--- a/lib/src/journal/file.c
+++ b/lib/src/journal/file.c
@@ -63,6 +63,9 @@ EDErrorCode ed_journal_file_parse(EDJournalFile *file, char const *filename)
     gchar *timestamp = NULL;
     gchar *index = NULL;
 
+    return_if_true(file == NULL, ed_error_args);
+    return_if_true(S_EMPTY(filename), ed_error_args);
+
     new_style = g_regex_new(
         "Journal\\.([\\dT\\-]+)\\.(\\d+)\\.log",
         0, 0, NULL