diff --git a/lib/vagrant/util/network_ip.rb b/lib/vagrant/util/network_ip.rb
index 1a4653656..8930bc36a 100644
--- a/lib/vagrant/util/network_ip.rb
+++ b/lib/vagrant/util/network_ip.rb
@@ -3,11 +3,21 @@ require "ipaddr"
 module Vagrant
   module Util
     module NetworkIP
+
+      DEFAULT_MASK = "255.255.255.0".freeze
+
+      LOGGER = Log4r::Logger.new("vagrant::util::NetworkIP")
+
       # Returns the network address of the given IP and subnet.
       #
       # @return [String]
       def network_address(ip, subnet)
-        IPAddr.new(ip).mask(subnet).to_s
+        begin
+          IPAddr.new(ip).mask(subnet).to_s
+        rescue IPAddr::InvalidPrefixError
+          LOGGER.warn("Provided mask '#{subnet}' is invalid. Falling back to using mask '#{DEFAULT_MASK}'")
+          IPAddr.new(ip).mask(DEFAULT_MASK).to_s
+        end
       end
     end
   end
diff --git a/test/unit/vagrant/util/network_ip_test.rb b/test/unit/vagrant/util/network_ip_test.rb
index 5351f4f9a..181b642cb 100644
--- a/test/unit/vagrant/util/network_ip_test.rb
+++ b/test/unit/vagrant/util/network_ip_test.rb
@@ -5,33 +5,47 @@ require "vagrant/util/network_ip"
 describe Vagrant::Util::NetworkIP do
   let(:klass) do
     Class.new do
-      extend Vagrant::Util::NetworkIP
+      include Vagrant::Util::NetworkIP
     end
   end
 
-  describe "network address" do
+  subject { klass.new }
+
+  describe "#network_address" do
     it "calculates it properly" do
-      expect(klass.network_address("192.168.2.234", "255.255.255.0")).to eq("192.168.2.0")
+      expect(subject.network_address("192.168.2.234", "255.255.255.0")).to eq("192.168.2.0")
     end
 
     it "calculates it properly with integer submask" do
-      expect(klass.network_address("192.168.2.234", "24")).to eq("192.168.2.0")
+      expect(subject.network_address("192.168.2.234", "24")).to eq("192.168.2.0")
     end
 
     it "calculates it properly with integer submask" do
-      expect(klass.network_address("192.168.2.234", 24)).to eq("192.168.2.0")
+      expect(subject.network_address("192.168.2.234", 24)).to eq("192.168.2.0")
     end
 
     it "calculates it properly for IPv6" do
-      expect(klass.network_address("fde4:8dba:82e1::c4", "64")).to eq("fde4:8dba:82e1::")
+      expect(subject.network_address("fde4:8dba:82e1::c4", "64")).to eq("fde4:8dba:82e1::")
     end
 
     it "calculates it properly for IPv6" do
-      expect(klass.network_address("fde4:8dba:82e1::c4", 64)).to eq("fde4:8dba:82e1::")
+      expect(subject.network_address("fde4:8dba:82e1::c4", 64)).to eq("fde4:8dba:82e1::")
     end
 
     it "calculates it properly for IPv6 for string mask" do
-      expect(klass.network_address("fde4:8dba:82e1::c4", "ffff:ffff:ffff:ffff::")).to eq("fde4:8dba:82e1::")
+      expect(subject.network_address("fde4:8dba:82e1::c4", "ffff:ffff:ffff:ffff::")).to eq("fde4:8dba:82e1::")
+    end
+
+    it "recovers from invalid netmask" do
+      # The mask function will produce an error for ruby >= 2.5
+      # If using a version of ruby that produces and error, then
+      # test to ensure `subject.network_address` produces expected
+      # results.
+      begin
+        IPAddr.new("192.168.2.234").mask("1.2.3.4")
+      rescue IPAddr::InvalidPrefixError
+        expect(subject.network_address("192.168.2.234", "1.2.3.4")).to eq("192.168.2.0")
+      end
     end
   end
 end