diff --git a/thoth-api/src/graphql/model.rs b/thoth-api/src/graphql/model.rs
index 394fa6e3..dcb722c0 100644
--- a/thoth-api/src/graphql/model.rs
+++ b/thoth-api/src/graphql/model.rs
@@ -3313,11 +3313,11 @@ impl Series {
     }
 
     pub fn issn_print(&self) -> Option<&String> {
-      self.issn_print.as_ref()
+        self.issn_print.as_ref()
     }
 
     pub fn issn_digital(&self) -> Option<&String> {
-      self.issn_digital.as_ref()
+        self.issn_digital.as_ref()
     }
 
     #[graphql(description = "URL of the series' landing page")]
diff --git a/thoth-export-server/src/marc21/marc21record_thoth.rs b/thoth-export-server/src/marc21/marc21record_thoth.rs
index 3f22f917..3dc8c350 100644
--- a/thoth-export-server/src/marc21/marc21record_thoth.rs
+++ b/thoth-export-server/src/marc21/marc21record_thoth.rs
@@ -635,10 +635,29 @@ impl Marc21Field<Marc21RecordThoth> for WorkIssues {
                     f.add_subfield(b"v", format!("vol. {}.", self.issue_ordinal).as_bytes())
                 })
                 .and_then(|f| f.add_subfield(b"x", self.series.issn_digital.as_deref().unwrap_or_default().as_bytes()))
-                .and_then(|f| f.add_subfield(b"x", self.series.issn_print.as_deref().unwrap_or_default().as_bytes()))
+                .and_then(|f| {
+                    f.add_subfield(
+                        b"x",
+                        self.series
+                            .issn_digital
+                            .as_deref()
+                            .unwrap_or_default()
+                            .as_bytes(),
+                    )
+                })
+                .and_then(|f| {
+                    f.add_subfield(
+                        b"x",
+                        self.series
+                            .issn_print
+                            .as_deref()
+                            .unwrap_or_default()
+                            .as_bytes(),
+                    )
+                })
                 .and_then(|f| builder.add_field(f))?;
-        }
-        Ok(())
+            }
+            Ok(())
     }
 }
 
diff --git a/thoth-export-server/src/xml/onix3_thoth.rs b/thoth-export-server/src/xml/onix3_thoth.rs
index aa68f0b2..8d3890a9 100644
--- a/thoth-export-server/src/xml/onix3_thoth.rs
+++ b/thoth-export-server/src/xml/onix3_thoth.rs
@@ -1150,7 +1150,7 @@ impl XmlElementBlock<Onix3Thoth> for WorkIssues {
                 })?;
                 write_element_block("IDValue", w, |w| {
                     w.write(XmlEvent::Characters(
-                        &self.series.issn_digital.replace('-', ""),
+                        &self.series.issn_digital.as_deref().unwrap_or_default().replace('-', ""),
                     ))
                     .map_err(|e| e.into())
                 })
@@ -1641,8 +1641,8 @@ mod tests {
             series: WorkIssuesSeries {
                 series_type: thoth_client::SeriesType::JOURNAL,
                 series_name: "Name of series".to_string(),
-                issn_print: "1234-5678".to_string(),
-                issn_digital: "8765-4321".to_string(),
+                issn_print: Some("1234-5678".to_string()),
+                issn_digital: Some("8765-4321".to_string()),
                 series_url: Some("https://series.url".to_string()),
                 series_description: None,
                 series_cfp_url: Some("https://series.cfp.url".to_string()),
@@ -1700,7 +1700,7 @@ mod tests {
         // Change all possible values to test that output is updated
         test_issue.issue_ordinal = 2;
         test_issue.series.series_name = "Different series".to_string();
-        test_issue.series.issn_digital = "1111-2222".to_string();
+        test_issue.series.issn_digital = Some("1111-2222".to_string());
         test_issue.series.series_url = None;
         test_issue.series.series_cfp_url = None;
         let output = generate_test_output(true, &test_issue);