diff --git a/bundler/lib/bundler/installer/parallel_installer.rb b/bundler/lib/bundler/installer/parallel_installer.rb
index c3bf5843b763..5b6680e5e12b 100644
--- a/bundler/lib/bundler/installer/parallel_installer.rb
+++ b/bundler/lib/bundler/installer/parallel_installer.rb
@@ -6,10 +6,11 @@
 module Bundler
   class ParallelInstaller
     class SpecInstallation
-      attr_accessor :spec, :name, :post_install_message, :state, :error
+      attr_accessor :spec, :name, :full_name, :post_install_message, :state, :error
       def initialize(spec)
         @spec = spec
         @name = spec.name
+        @full_name = spec.full_name
         @state = :none
         @post_install_message = ""
         @error = nil
@@ -49,14 +50,11 @@ def dependencies_installed?(all_specs)
       # Represents only the non-development dependencies, the ones that are
       # itself and are in the total list.
       def dependencies
-        @dependencies ||= begin
-          all_dependencies.reject {|dep| ignorable_dependency? dep }
-        end
+        @dependencies ||= all_dependencies.reject {|dep| ignorable_dependency? dep }
       end
 
       def missing_lockfile_dependencies(all_spec_names)
-        deps = all_dependencies.reject {|dep| ignorable_dependency? dep }
-        deps.reject {|dep| all_spec_names.include? dep.name }
+        dependencies.reject {|dep| all_spec_names.include? dep.name }
       end
 
       # Represents all dependencies
@@ -65,7 +63,7 @@ def all_dependencies
       end
 
       def to_s
-        "#<#{self.class} #{@spec.full_name} (#{state})>"
+        "#<#{self.class} #{full_name} (#{state})>"
       end
     end
 
@@ -99,12 +97,37 @@ def call
         install_serially
       end
 
+      check_for_unmet_dependencies
+
       handle_error if failed_specs.any?
       @specs
     ensure
       worker_pool && worker_pool.stop
     end
 
+    def check_for_unmet_dependencies
+      unmet_dependencies = @specs.map do |s|
+        [
+          s,
+          s.dependencies.reject {|dep| @specs.any? {|spec| dep.matches_spec?(spec.spec) } },
+        ]
+      end.reject {|a| a.last.empty? }
+      return if unmet_dependencies.empty?
+
+      warning = []
+      warning << "Your lockfile doesn't include a valid resolution."
+      warning << "You can fix this by regenerating your lockfile or trying to manually editing the bad locked gems to a version that satisfies all dependencies."
+      warning << "The unmet dependencies are:"
+
+      unmet_dependencies.each do |spec, unmet_spec_dependencies|
+        unmet_spec_dependencies.each do |unmet_spec_dependency|
+          warning << "* #{unmet_spec_dependency}, depended upon #{spec.full_name}, unsatisfied by #{@specs.find {|s| s.name == unmet_spec_dependency.name && !unmet_spec_dependency.matches_spec?(s.spec) }.full_name}"
+        end
+      end
+
+      Bundler.ui.warn(warning.join("\n"))
+    end
+
     def check_for_corrupt_lockfile
       missing_dependencies = @specs.map do |s|
         [
diff --git a/bundler/spec/bundler/installer/parallel_installer_spec.rb b/bundler/spec/bundler/installer/parallel_installer_spec.rb
index ace5c1a23a9a..e680633862ab 100644
--- a/bundler/spec/bundler/installer/parallel_installer_spec.rb
+++ b/bundler/spec/bundler/installer/parallel_installer_spec.rb
@@ -44,4 +44,37 @@
       end
     end
   end
+
+  context "when the spec set is not a valid resolution" do
+    let(:all_specs) do
+      [
+        build_spec("cucumber", "4.1.0") {|s| s.runtime "diff-lcs", "< 1.4" },
+        build_spec("diff-lcs", "1.4.4"),
+      ].flatten
+    end
+
+    it "prints a warning" do
+      expect(Bundler.ui).to receive(:warn).with(<<-W.strip)
+Your lockfile doesn't include a valid resolution.
+You can fix this by regenerating your lockfile or trying to manually editing the bad locked gems to a version that satisfies all dependencies.
+The unmet dependencies are:
+* diff-lcs (< 1.4), depended upon cucumber-4.1.0, unsatisfied by diff-lcs-1.4.4
+      W
+      subject.check_for_unmet_dependencies
+    end
+  end
+
+  context "when the spec set is a valid resolution" do
+    let(:all_specs) do
+      [
+        build_spec("cucumber", "4.1.0") {|s| s.runtime "diff-lcs", "< 1.4" },
+        build_spec("diff-lcs", "1.3"),
+      ].flatten
+    end
+
+    it "doesn't print a warning" do
+      expect(Bundler.ui).not_to receive(:warn)
+      subject.check_for_unmet_dependencies
+    end
+  end
 end
diff --git a/bundler/spec/bundler/installer/spec_installation_spec.rb b/bundler/spec/bundler/installer/spec_installation_spec.rb
index a9cf09a37296..e63ef26cb316 100644
--- a/bundler/spec/bundler/installer/spec_installation_spec.rb
+++ b/bundler/spec/bundler/installer/spec_installation_spec.rb
@@ -8,6 +8,10 @@
     def a_spec.name
       "I like tests"
     end
+
+    def a_spec.full_name
+      "I really like tests"
+    end
     a_spec
   end
 
diff --git a/dev_gems.rb.lock b/dev_gems.rb.lock
index 09c4dee806a8..272adbba14d9 100644
--- a/dev_gems.rb.lock
+++ b/dev_gems.rb.lock
@@ -3,7 +3,7 @@ GEM
   specs:
     addressable (2.7.0)
       public_suffix (>= 2.0.2, < 5.0)
-    ast (2.4.0)
+    ast (2.4.2)
     aws-eventstream (1.1.0)
     aws-partitions (1.411.0)
     aws-sdk-core (3.110.0)