diff --git a/src/parser.js b/src/parser.js
index 283f7df..54b38e2 100644
--- a/src/parser.js
+++ b/src/parser.js
@@ -399,6 +399,12 @@ class Parser {
     let comparableVersion = version;
     let isLoose = false;
 
+    const currentBrowserVersion = this.getBrowserVersion();
+
+    if (typeof currentBrowserVersion !== 'string') {
+      return void 0;
+    }
+
     if (version[0] === '>') {
       expectedResult = 1;
       comparableVersion = version.substr(1);
@@ -412,7 +418,7 @@ class Parser {
       comparableVersion = version.substr(1);
     }
 
-    return compareVersions(this.getBrowserVersion(), comparableVersion, isLoose) === expectedResult;
+    return compareVersions(currentBrowserVersion, comparableVersion, isLoose) === expectedResult;
   }
 
   isOS(osName) {
diff --git a/test/acceptance/useragentstrings.yml b/test/acceptance/useragentstrings.yml
index 1781c34..a874af3 100644
--- a/test/acceptance/useragentstrings.yml
+++ b/test/acceptance/useragentstrings.yml
@@ -984,6 +984,20 @@
         engine: 
           name: "WebKit"
           version: "601.1.46"
+    - ua: "Mozilla/5.0 (iPhone; CPU iPhone OS 11_4_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Mobile/15G77 [FBAN/FBIOS;FBDV/iPhone7,2;FBMD/iPhone;FBSN/iOS;FBSV/11.4.1;FBSS/2;FBCR/vfnl;FBID/phone;FBLC/nl_NL;FBOP/5;FBRV/0]"
+      spec:
+        browser:
+          name: "Safari"
+        os:
+          name: "iOS"
+          version: "11.4.1"
+        platform:
+          type: "mobile"
+          vendor: "Apple"
+          model: "iPhone"
+        engine:
+          name: "WebKit"
+          version: "605.1.15"
   Internet Explorer: 
     - 
       ua: "Mozilla/5.0 (Windows NT 6.3; Win64; x64; Trident/7.0; MAARJS; rv:11.0) like Gecko"
diff --git a/test/unit/parser.js b/test/unit/parser.js
index 5e37a0b..53abe4c 100644
--- a/test/unit/parser.js
+++ b/test/unit/parser.js
@@ -57,7 +57,7 @@ test('Skip parsing shouldn\'t parse', (t) => {
   t.deepEqual((new Parser(UA, true)).getResult(), {});
 });
 
-test('Parser.check should make simple comparisons', (t) => {
+test('Parser.satisfies should make simple comparisons', (t) => {
   // also covers Parser.compareVersion() method
   t.is(parser.satisfies({ opera: '>42' }), true);
   t.is(parser.satisfies({ opera: '<44' }), true);
@@ -66,7 +66,7 @@ test('Parser.check should make simple comparisons', (t) => {
   t.is(parser.satisfies({ opera: '~43' }), true);
 });
 
-test('Parser.check should make complex comparison', (t) => {
+test('Parser.satisfies should make complex comparison', (t) => {
   t.is(parser.satisfies({
     macos: {
       safari: '>11',
@@ -78,7 +78,7 @@ test('Parser.check should make complex comparison', (t) => {
   }), true);
 });
 
-test('Parser.check should respect platform and OS specific declarations', (t) => {
+test('Parser.satisfies should respect platform and OS specific declarations', (t) => {
   t.is(parser.satisfies({
     macos: {
       opera: '>45',
@@ -114,6 +114,14 @@ test('Parser.check should respect platform and OS specific declarations', (t) =>
   }), void 0);
 });
 
+test('Parser.satisfies for versionless UA strings', (t) => {
+  const _parser = new Parser('Mozilla/5.0 (iPhone; CPU iPhone OS 11_4_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Mobile/15G77 [FBAN/FBIOS;FBDV/iPhone7,2;FBMD/iPhone;FBSN/iOS;FBSV/11.4.1;FBSS/2;FBCR/vfnl;FBID/phone;FBLC/nl_NL;FBOP/5;FBRV/0]');
+
+  t.is(_parser.satisfies({
+    safari: '>9',
+  }), void 0);
+});
+
 test('Parser.is should pass', (t) => {
   t.is(parser.is('opera'), true);
   t.is(parser.is('desktop'), true);