diff --git a/src/csl/sort.rs b/src/csl/sort.rs
index 1c8ab83..bcf9380 100644
--- a/src/csl/sort.rs
+++ b/src/csl/sort.rs
@@ -27,10 +27,10 @@ impl<'a> StyleContext<'a> {
             SortKey::Variable { variable: Variable::Standard(s), .. } => {
                 let a = InstanceContext::sort_instance(a, a_idx)
                     .resolve_standard_variable(LongShortForm::default(), *s)
-                    .map(|s| s.to_string());
+                    .map(|s| s.to_string().to_lowercase());
                 let b = InstanceContext::sort_instance(b, b_idx)
                     .resolve_standard_variable(LongShortForm::default(), *s)
-                    .map(|s| s.to_string());
+                    .map(|s| s.to_string().to_lowercase());
 
                 a.cmp(&b)
             }
diff --git a/tests/citeproc-pass.txt b/tests/citeproc-pass.txt
index fcbbe72..c10d743 100644
--- a/tests/citeproc-pass.txt
+++ b/tests/citeproc-pass.txt
@@ -292,6 +292,7 @@ position_TrueInCitation
 punctuation_DateStripPeriods
 punctuation_DoNotSuppressColonAfterPeriod
 punctuation_NoSuppressOfPeriodBeforeSemicolon
+sort_CaseInsensitiveCitation
 sort_Citation
 sort_CitationSecondaryKey
 sort_CiteGroupDelimiter