diff --git a/lib/bundler/vendor/pub_grub/lib/pub_grub/basic_package_source.rb b/lib/bundler/vendor/pub_grub/lib/pub_grub/basic_package_source.rb
index dce20d37ad..27f0e39d4c 100644
--- a/lib/bundler/vendor/pub_grub/lib/pub_grub/basic_package_source.rb
+++ b/lib/bundler/vendor/pub_grub/lib/pub_grub/basic_package_source.rb
@@ -164,7 +164,7 @@ module Bundler::PubGrub
             sorted_versions[high]
           end
 
-        range = VersionRange.new(min: low, max: high, include_min: true)
+        range = VersionRange.new(min: low, max: high, include_min: !low.nil?)
 
         self_constraint = VersionConstraint.new(package, range: range)
 
diff --git a/lib/bundler/vendor/pub_grub/lib/pub_grub/version_range.rb b/lib/bundler/vendor/pub_grub/lib/pub_grub/version_range.rb
index 8d73c3f7b5..49dcf716a3 100644
--- a/lib/bundler/vendor/pub_grub/lib/pub_grub/version_range.rb
+++ b/lib/bundler/vendor/pub_grub/lib/pub_grub/version_range.rb
@@ -76,6 +76,9 @@ module Bundler::PubGrub
     end
 
     def initialize(min: nil, max: nil, include_min: false, include_max: false, name: nil)
+      raise ArgumentError, "Ranges without a lower bound cannot have include_min == true" if !min && include_min == true
+      raise ArgumentError, "Ranges without an upper bound cannot have include_max == true" if !max && include_max == true
+
       @min = min
       @max = max
       @include_min = include_min
@@ -311,10 +314,19 @@ module Bundler::PubGrub
 
     def contiguous_to?(other)
       return false if other.empty?
+      return true if any?
 
-      intersects?(other) ||
-        (min == other.max && (include_min || other.include_max)) ||
-        (max == other.min && (include_max || other.include_min))
+      intersects?(other) || contiguous_below?(other) || contiguous_above?(other)
+    end
+
+    def contiguous_below?(other)
+      return false if !max || !other.min
+
+      max == other.min && (include_max || other.include_min)
+    end
+
+    def contiguous_above?(other)
+      other.contiguous_below?(self)
     end
 
     def allows_all?(other)
@@ -375,15 +387,15 @@ module Bundler::PubGrub
     def invert
       return self.class.empty if any?
 
-      low = VersionRange.new(max: min, include_max: !include_min)
-      high = VersionRange.new(min: max, include_min: !include_max)
+      low = -> { VersionRange.new(max: min, include_max: !include_min) }
+      high = -> { VersionRange.new(min: max, include_min: !include_max) }
 
       if !min
-        high
+        high.call
       elsif !max
-        low
+        low.call
       else
-        low.union(high)
+        low.call.union(high.call)
       end
     end
 
diff --git a/lib/bundler/vendor/pub_grub/lib/pub_grub/version_solver.rb b/lib/bundler/vendor/pub_grub/lib/pub_grub/version_solver.rb
index 4caf6b355b..b56b8ce43e 100644
--- a/lib/bundler/vendor/pub_grub/lib/pub_grub/version_solver.rb
+++ b/lib/bundler/vendor/pub_grub/lib/pub_grub/version_solver.rb
@@ -36,26 +36,25 @@ module Bundler::PubGrub
 
     # Returns true if there is more work to be done, false otherwise
     def work
-      return false if solved?
-
-      next_package = choose_package_version
-      propagate(next_package)
-
-      if solved?
+      unsatisfied_terms = solution.unsatisfied
+      if unsatisfied_terms.empty?
         logger.info { "Solution found after #{solution.attempted_solutions} attempts:" }
         solution.decisions.each do |package, version|
           next if Package.root?(package)
           logger.info { "* #{package} #{version}" }
         end
 
-        false
-      else
-        true
+        return false
       end
+
+      next_package = choose_package_version_from(unsatisfied_terms)
+      propagate(next_package)
+
+      true
     end
 
     def solve
-      work until solved?
+      while work; end
 
       solution.decisions
     end
@@ -105,25 +104,21 @@ module Bundler::PubGrub
       unsatisfied.package
     end
 
-    def next_package_to_try
-      solution.unsatisfied.min_by do |term|
+    def next_term_to_try_from(unsatisfied_terms)
+      unsatisfied_terms.min_by do |term|
         package = term.package
         range = term.constraint.range
         matching_versions = source.versions_for(package, range)
         higher_versions = source.versions_for(package, range.upper_invert)
 
         [matching_versions.count <= 1 ? 0 : 1, higher_versions.count]
-      end.package
+      end
     end
 
-    def choose_package_version
-      if solution.unsatisfied.empty?
-        logger.info "No packages unsatisfied. Solving complete!"
-        return nil
-      end
+    def choose_package_version_from(unsatisfied_terms)
+      unsatisfied_term = next_term_to_try_from(unsatisfied_terms)
+      package = unsatisfied_term.package
 
-      package = next_package_to_try
-      unsatisfied_term = solution.unsatisfied.find { |t| t.package == package }
       version = source.versions_for(package, unsatisfied_term.constraint.range).first
       logger.debug { "attempting #{package} #{version}" }
 
diff --git a/tool/bundler/vendor_gems.rb b/tool/bundler/vendor_gems.rb
index bef955655f..16fe53a5d8 100644
--- a/tool/bundler/vendor_gems.rb
+++ b/tool/bundler/vendor_gems.rb
@@ -8,7 +8,7 @@ gem "net-http", "0.6.0"
 gem "net-http-persistent", "4.0.4"
 gem "net-protocol", "0.2.2"
 gem "optparse", "0.6.0"
-gem "pub_grub", github: "jhawthorn/pub_grub"
+gem "pub_grub", github: "jhawthorn/pub_grub", ref: "57d4f344366c8b86f7fe506e9bfa08f3c731e397"
 gem "resolv", "0.6.0"
 gem "securerandom", "0.4.1"
 gem "timeout", "0.4.3"
diff --git a/tool/bundler/vendor_gems.rb.lock b/tool/bundler/vendor_gems.rb.lock
index 3c3ec50832..79eca0e7c0 100644
--- a/tool/bundler/vendor_gems.rb.lock
+++ b/tool/bundler/vendor_gems.rb.lock
@@ -6,7 +6,8 @@ GIT
 
 GIT
   remote: https://github.com/jhawthorn/pub_grub.git
-  revision: 55a2d65c5c3176f72de5e25d59fb6f52b9fe60ef
+  revision: 57d4f344366c8b86f7fe506e9bfa08f3c731e397
+  ref: 57d4f344366c8b86f7fe506e9bfa08f3c731e397
   specs:
     pub_grub (0.5.0)