diff --git a/CHANGELOG.md b/CHANGELOG.md
index ed83cfb..047ab68 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,10 @@
 This log documents significant changes for each release.  This project follows
 [Semantic Versioning](http://semver.org/).
 
+## [2.5.0] - 2020-08-26
+### Added
+- Function union(other: collection)
+
 ## [2.4.0] - 2020-08-05
 ### Added
 - Support for DSTU2 model
diff --git a/package-lock.json b/package-lock.json
index c4a15fb..d49a3b9 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "fhirpath",
-  "version": "2.4.0",
+  "version": "2.5.0",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
@@ -4424,12 +4424,12 @@
       }
     },
     "fhir": {
-      "version": "4.7.9",
-      "resolved": "https://registry.npmjs.org/fhir/-/fhir-4.7.9.tgz",
-      "integrity": "sha512-f8cpFML+/8RxnDLmbsyxB40D0qqPmjrDt7Qa5gBAnyEnhRietAnxRSp7hZ1BeBosnJ24FjfqCh+e1hcp1oEA3A==",
+      "version": "4.7.10",
+      "resolved": "https://registry.npmjs.org/fhir/-/fhir-4.7.10.tgz",
+      "integrity": "sha512-sLYnMSFNlZ8xhgnVJogasH3Tt0rs5D5hn4lXaq12HZFRsaCVTEty/Yngphj+0/wuowRS0xj/PPQj7P3Nr/Kz7g==",
       "dev": true,
       "requires": {
-        "lodash": "^4.17.14",
+        "lodash": "^4.17.19",
         "path": "^0.12.7",
         "q": "^1.4.1",
         "randomatic": "^3.1.0",
@@ -4442,7 +4442,7 @@
           "dev": true
         },
         "lodash": {
-          "version": "4.17.15",
+          "version": "4.17.19",
           "bundled": true,
           "dev": true
         },
diff --git a/package.json b/package.json
index 7f19633..dec151b 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "fhirpath",
-  "version": "2.4.0",
+  "version": "2.5.0",
   "description": "A FHIRPath engine",
   "main": "src/fhirpath.js",
   "dependencies": {
@@ -18,7 +18,7 @@
     "bestzip": "^2.1.4",
     "copy-webpack-plugin": "^6.0.3",
     "eslint": "^5.2.0",
-    "fhir": "^4.7.9",
+    "fhir": "^4.7.10",
     "grunt": "^1.1.0",
     "grunt-cli": "^1.3.1",
     "grunt-contrib-connect": "^2.0.0",
diff --git a/src/combining.js b/src/combining.js
index eb43ade..b3958d2 100644
--- a/src/combining.js
+++ b/src/combining.js
@@ -3,7 +3,7 @@
 var combineFns = {};
 var existence = require('./existence');
 
-combineFns.unionOp = function(coll1, coll2){
+combineFns.union = function(coll1, coll2){
   return existence.distinctFn(coll1.concat(coll2));
 };
 
diff --git a/src/fhirpath.js b/src/fhirpath.js
index 8ade332..aa25552 100644
--- a/src/fhirpath.js
+++ b/src/fhirpath.js
@@ -82,6 +82,7 @@ engine.invocationTable = {
   take:         {fn: filtering.takeFn, arity: {1: ["Integer"]}},
   skip:         {fn: filtering.skipFn, arity: {1: ["Integer"]}},
   combine:      {fn: combining.combineFn, arity: {1: ["AnyAtRoot"]}},
+  union:        {fn: combining.union,   arity: {1: ["AnyAtRoot"]}},
   iif:          {fn: misc.iifMacro,    arity: {2: ["Expr", "Expr"], 3: ["Expr", "Expr", "Expr"]}},
   trace:        {fn: misc.traceFn,     arity: {0: [], 1: ["String"]}},
   toInteger:    {fn: misc.toInteger},
@@ -127,7 +128,7 @@ engine.invocationTable = {
   children:        {fn: navigation.children },
   descendants:     {fn: navigation.descendants },
 
-  "|":          {fn: combining.unionOp,   arity: {2: ["Any", "Any"]}},
+  "|":          {fn: combining.union,   arity: {2: ["Any", "Any"]}},
   "=":          {fn: equality.equal,   arity: {2: ["Any", "Any"]}, nullable: true},
   "!=":         {fn: equality.unequal,   arity: {2: ["Any", "Any"]}, nullable: true},
   "~":          {fn: equality.equival,   arity: {2: ["Any", "Any"]}},
diff --git a/test/cases/fhir-r4.yaml b/test/cases/fhir-r4.yaml
index 65265a0..8ae750d 100644
--- a/test/cases/fhir-r4.yaml
+++ b/test/cases/fhir-r4.yaml
@@ -2834,13 +2834,11 @@ tests:
         expression: 1.union(2).union(3).count() = 3
         result:
           - true
-        disable: true
       - desc: '** testUnion5'
         inputfile: patient-example.json
         expression: 1.union(2.union(3)).count() = 3
         result:
           - true
-        disable: true
       - desc: '** testUnion6'
         inputfile: patient-example.json
         expression: (1 | 2).combine(2).count() = 3
@@ -2856,7 +2854,6 @@ tests:
         expression: 1.combine(1).union(2).count() = 2
         result:
           - true
-        disable: true
   - 'group: testIntersect':
       - desc: '** testIntersect1'
         inputfile: patient-example.json