diff --git a/src/PhoneNumbers/ParseOptionsExtensions.cs b/src/PhoneNumbers/ParseOptionsExtensions.cs
index a824890b..f8b90bbc 100644
--- a/src/PhoneNumbers/ParseOptionsExtensions.cs
+++ b/src/PhoneNumbers/ParseOptionsExtensions.cs
@@ -89,9 +89,14 @@ public static ParseOptions AllowUnitedKingdomNumberingPlanCountries(this ParseOp
 
     private static ParseOptions Allow(ParseOptions parseOptions, Func<CountryInfo, bool> predicate)
     {
+        if (parseOptions is null)
+        {
+            throw new ArgumentNullException(nameof(parseOptions));
+        }
+
         foreach (var countryInfo in CountryInfo.GetCountries(predicate))
         {
-            parseOptions?.Countries.Add(countryInfo);
+            parseOptions.Countries.Add(countryInfo);
         }
 
         return parseOptions;
diff --git a/test/PhoneNumbers.Tests/ParseOptionsTests.cs b/test/PhoneNumbers.Tests/ParseOptionsTests.cs
index 5acbfc80..1de5ecf2 100644
--- a/test/PhoneNumbers.Tests/ParseOptionsTests.cs
+++ b/test/PhoneNumbers.Tests/ParseOptionsTests.cs
@@ -125,6 +125,22 @@ public void Default()
         Assert.Equal(countryInfos, ParseOptions.Default.Countries);
     }
 
+    [Fact]
+    public void Extensions_Throw_If_ParseOptions_Null()
+    {
+        var parseOptions = default(ParseOptions);
+
+        typeof(ParseOptionsExtensions)
+            .GetMethods(BindingFlags.Static | BindingFlags.Public)
+            .Where(x => x.GetParameters().Length == 1 && x.GetParameters()[0].ParameterType == typeof(ParseOptions))
+            .ToList()
+            .ForEach(x =>
+            {
+                var exception = Assert.Throws<TargetInvocationException>(() => x.Invoke(null, new [] { parseOptions }));
+                Assert.IsType<ArgumentNullException>(exception.InnerException);
+            });
+    }
+
     [Fact]
     public void GetCountryInfo_Does_Not_Exist() =>
         Assert.Null(ParseOptions.Default.GetCountryInfo("ZZ"));