diff --git a/ui/src/criteria/filterableGroup.tsx b/ui/src/criteria/filterableGroup.tsx
index 87ad04e3b..e83380030 100644
--- a/ui/src/criteria/filterableGroup.tsx
+++ b/ui/src/criteria/filterableGroup.tsx
@@ -1190,16 +1190,43 @@ function generateFilters(
         },
       });
     } else {
-      operands.push({
-        filterType: tanagra.FilterFilterTypeEnum.Attribute,
-        filterUnion: {
-          attributeFilter: {
-            attribute: vd.attribute,
-            operator: tanagra.AttributeFilterOperatorEnum.In,
-            values: vd.selected.map((s) => literalFromDataValue(s.value)),
+      const operandFilter: tanagra.Filter[] = [
+        {
+          filterType: tanagra.FilterFilterTypeEnum.Attribute,
+          filterUnion: {
+            attributeFilter: {
+              attribute: vd.attribute,
+              operator: tanagra.AttributeFilterOperatorEnum.In,
+              values: [],
+            },
           },
         },
+      ];
+
+      vd.selected.forEach((s) => {
+        const sLiteral = literalFromDataValue(s.value);
+        if (s.value === null) {
+          // 'n/a' is selected: entries with no value for this attribute
+          operandFilter.push({
+            filterType: tanagra.FilterFilterTypeEnum.Attribute,
+            filterUnion: {
+              attributeFilter: {
+                attribute: vd.attribute,
+                operator: tanagra.AttributeFilterOperatorEnum.IsEmptyString,
+              },
+            },
+          });
+        } else {
+          operandFilter[0].filterUnion?.attributeFilter?.values?.push(sLiteral);
+        }
       });
+
+      operands.push(
+        makeBooleanLogicFilter(
+          tanagra.BooleanLogicFilterOperatorEnum.Or,
+          operandFilter
+        ) as tanagra.Filter
+      );
     }
   });
 
diff --git a/ui/src/data/source.tsx b/ui/src/data/source.tsx
index fbeff42cc..5eb3bb5f8 100644
--- a/ui/src/data/source.tsx
+++ b/ui/src/data/source.tsx
@@ -1606,9 +1606,9 @@ function isInternalAttribute(attribute: string): boolean {
 }
 
 export function literalFromDataValue(value: DataValue): tanagra.Literal {
-  let dataType = tanagra.DataType.String;
-  if (typeof value === "bigint") {
-    dataType = tanagra.DataType.Int64;
+  let dataType = tanagra.DataType.Int64;
+  if (typeof value === "string") {
+    dataType = tanagra.DataType.String;
   } else if (typeof value === "boolean") {
     dataType = tanagra.DataType.Boolean;
   } else if (value instanceof Date) {