diff --git a/packages/fhir-qb/index.js b/packages/fhir-qb/index.js
index 6b5178d..9aacd63 100644
--- a/packages/fhir-qb/index.js
+++ b/packages/fhir-qb/index.js
@@ -494,7 +494,7 @@ class QueryBuilder {
 		// If the modifier is 'missing', nothing else matters, we're just checking if the field exists.
 		if (modifier === matchModifiers.missing) {
 			value = sanitize.sanitizeBoolean({ field, value });
-			subQuery = this.qb.buildExistsQuery({ field, exists: value });
+			subQuery = this.qb.buildExistsQuery({ field, exists: !value });
 		} else {
 			// Otherwise, construct a query based on data type
 			switch (type) {
diff --git a/packages/fhir-qb/index.test.js b/packages/fhir-qb/index.test.js
index ced2ca8..9b8e1f0 100644
--- a/packages/fhir-qb/index.test.js
+++ b/packages/fhir-qb/index.test.js
@@ -4641,7 +4641,7 @@ describe('Mongo Tests', () => {
 				includeArchived,
 			});
 			const expectedResult = [
-				{ $match: { $and: [{ $or: [{ foo: { $exists: true } }] }] } },
+				{ $match: { $and: [{ $or: [{ foo: { $exists: false } }] }] } },
 				{ $match: { 'meta._isArchived': false } },
 				{
 					$facet: {
@@ -4678,7 +4678,7 @@ describe('Mongo Tests', () => {
 				includeArchived,
 			});
 			const expectedResult = [
-				{ $match: { $and: [{ $or: [{ foo: { $exists: false } }] }] } },
+				{ $match: { $and: [{ $or: [{ foo: { $exists: true } }] }] } },
 				{ $match: { 'meta._isArchived': false } },
 				{
 					$facet: {