diff --git a/pkg/installer/installer.go b/pkg/installer/installer.go
index 98fb1612..f0498f98 100644
--- a/pkg/installer/installer.go
+++ b/pkg/installer/installer.go
@@ -106,23 +106,39 @@ func (l *LuetInstaller) Upgrade(s *System) error {
 		return err
 	}
 	// First match packages against repositories by priority
-	//	matches := syncedRepos.PackageMatches(p)
 	allRepos := pkg.NewInMemoryDatabase(false)
 	syncedRepos.SyncDatabase(allRepos)
 	// compute a "big" world
 	solv := solver.NewResolver(s.Database, allRepos, pkg.NewInMemoryDatabase(false), l.Options.SolverOptions.Resolver())
-	uninstall, solution, err := solv.Upgrade()
+	uninstall, solution, err := solv.Upgrade(false)
 	if err != nil {
 		return errors.Wrap(err, "Failed solving solution for upgrade")
 	}
 
+	// We don't want any conflict with the installed to raise during the upgrade.
+	// In this way we both force uninstalls and we avoid to check with conflicts
+	// against the current system state which is pending to deletion
+	// E.g. you can't check for conflicts for an upgrade of a new version of A
+	// if the old A results installed in the system. This is due to the fact that
+	// now the solver enforces the constraints and explictly denies two packages
+	// of the same version installed.
+	forced := false
+	if l.Options.Force {
+		forced = true
+	}
+	l.Options.Force = true
+
 	for _, u := range uninstall {
+		Info(":package: Marked for deletion", u.HumanReadableString())
+
 		err := l.Uninstall(u, s)
 		if err != nil && !l.Options.Force {
 			Error("Failed uninstall for ", u.HumanReadableString())
 			return errors.Wrap(err, "uninstalling "+u.HumanReadableString())
 		}
+
 	}
+	l.Options.Force = forced
 
 	toInstall := []pkg.Package{}
 	for _, assertion := range solution {
@@ -249,29 +265,27 @@ func (l *LuetInstaller) Install(cp []pkg.Package, s *System) error {
 	close(all)
 	wg.Wait()
 
+	for _, c := range toInstall {
+		// Annotate to the system that the package was installed
+		_, err := s.Database.CreatePackage(c.Package)
+		if err != nil && !l.Options.Force {
+			return errors.Wrap(err, "Failed creating package")
+		}
+	}
 	executedFinalizer := map[string]bool{}
 
 	// TODO: Lower those errors as warning
 	for _, w := range p {
 		// Finalizers needs to run in order and in sequence.
 		ordered := solution.Order(allRepos, w.GetFingerPrint())
+	ORDER:
 		for _, ass := range ordered {
 			if ass.Value {
-				// Annotate to the system that the package was installed
-				if _, err := s.Database.FindPackage(ass.Package); err == nil {
-					err := s.Database.UpdatePackage(ass.Package)
-					if err != nil && !l.Options.Force {
-						return errors.Wrap(err, "Failed updating package")
-					}
-				} else {
-					_, err := s.Database.CreatePackage(ass.Package)
-					if err != nil && !l.Options.Force {
-						return errors.Wrap(err, "Failed creating package")
-					}
-				}
+
 				installed, ok := toInstall[ass.Package.GetFingerPrint()]
 				if !ok {
-					return errors.New("Couldn't find ArtifactMatch for " + ass.Package.HumanReadableString())
+					// It was a dep already installed in the system, so we can skip it safely
+					continue ORDER
 				}
 
 				treePackage, err := installed.Repository.GetTree().GetDatabase().FindPackage(ass.Package)
@@ -381,12 +395,17 @@ func (l *LuetInstaller) uninstall(p pkg.Package, s *System) error {
 }
 
 func (l *LuetInstaller) Uninstall(p pkg.Package, s *System) error {
-	// compute uninstall from all world - remove packages in parallel - run uninstall finalizer (in order) - mark the uninstallation in db
+	// compute uninstall from all world - remove packages in parallel - run uninstall finalizer (in order) TODO - mark the uninstallation in db
 	// Get installed definition
 
+	checkConflicts := true
+	if l.Options.Force == true {
+		checkConflicts = false
+	}
+
 	if !l.Options.NoDeps {
 		solv := solver.NewResolver(s.Database, s.Database, pkg.NewInMemoryDatabase(false), l.Options.SolverOptions.Resolver())
-		solution, err := solv.Uninstall(p)
+		solution, err := solv.Uninstall(p, checkConflicts)
 		if err != nil && !l.Options.Force {
 			return errors.Wrap(err, "Could not solve the uninstall constraints. Tip: try with --solver-type qlearning or with --force, or by removing packages excluding their dependencies with --nodeps")
 		}
diff --git a/pkg/package/package.go b/pkg/package/package.go
index 08e197b1..0887df5b 100644
--- a/pkg/package/package.go
+++ b/pkg/package/package.go
@@ -479,7 +479,7 @@ func (pack *DefaultPackage) BuildFormula(definitiondb PackageDatabase, db Packag
 			}
 			B := bf.Var(encodedB)
 			if !p.Matches(cp) {
-				formulas = append(formulas, bf.Or(A, bf.Or(bf.Not(A), bf.Not(B))))
+				formulas = append(formulas, bf.Or(bf.Not(A), bf.Or(bf.Not(A), bf.Not(B))))
 			}
 		}
 	}
@@ -495,62 +495,60 @@ func (pack *DefaultPackage) BuildFormula(definitiondb PackageDatabase, db Packag
 			if err != nil || len(packages) == 0 {
 				required = requiredDef
 			} else {
-				if len(packages) == 1 {
-					required = packages[0]
-				} else {
-					var ALO, priorityConstraints, priorityALO []bf.Formula
 
-					// Try to prio best match
-					// Force the solver to consider first our candidate (if does exists).
-					// Then builds ALO and AMO for the requires.
-					c, candidateErr := definitiondb.FindPackageCandidate(requiredDef)
-					var C bf.Formula
-					if candidateErr == nil {
-						// We have a desired candidate, try to look a solution with that included first
-						for _, o := range packages {
-							encodedB, err := o.Encode(db)
-							if err != nil {
-								return nil, err
-							}
-							B := bf.Var(encodedB)
-							if !o.Matches(c) {
-								priorityConstraints = append(priorityConstraints, bf.Not(B))
-								priorityALO = append(priorityALO, B)
-							}
-						}
-						encodedC, err := c.Encode(db)
-						if err != nil {
-							return nil, err
-						}
-						C = bf.Var(encodedC)
-						// Or the Candidate is true, or all the others might be not true
-						// This forces the CDCL sat implementation to look first at a solution with C=true
-						formulas = append(formulas, bf.Or(bf.Or(C, bf.Or(priorityConstraints...)), bf.Or(bf.Not(C), bf.Or(priorityALO...))))
-					}
+				var ALO, priorityConstraints, priorityALO []bf.Formula
 
-					// AMO - At most one
+				// Try to prio best match
+				// Force the solver to consider first our candidate (if does exists).
+				// Then builds ALO and AMO for the requires.
+				c, candidateErr := definitiondb.FindPackageCandidate(requiredDef)
+				var C bf.Formula
+				if candidateErr == nil {
+					// We have a desired candidate, try to look a solution with that included first
 					for _, o := range packages {
 						encodedB, err := o.Encode(db)
 						if err != nil {
 							return nil, err
 						}
 						B := bf.Var(encodedB)
-						ALO = append(ALO, B)
-						for _, i := range packages {
-							encodedI, err := i.Encode(db)
-							if err != nil {
-								return nil, err
-							}
-							I := bf.Var(encodedI)
-							if !o.Matches(i) {
-								formulas = append(formulas, bf.Or(bf.Not(I), bf.Not(B)))
-							}
+						if !o.Matches(c) {
+							priorityConstraints = append(priorityConstraints, bf.Not(B))
+							priorityALO = append(priorityALO, B)
 						}
 					}
-					formulas = append(formulas, bf.Or(ALO...)) // ALO - At least one
-					continue
+					encodedC, err := c.Encode(db)
+					if err != nil {
+						return nil, err
+					}
+					C = bf.Var(encodedC)
+					// Or the Candidate is true, or all the others might be not true
+					// This forces the CDCL sat implementation to look first at a solution with C=true
+					formulas = append(formulas, bf.Or(bf.Not(A), bf.Or(bf.Or(C, bf.Or(priorityConstraints...)), bf.Or(bf.Not(C), bf.Or(priorityALO...)))))
 				}
+
+				// AMO - At most one
+				for _, o := range packages {
+					encodedB, err := o.Encode(db)
+					if err != nil {
+						return nil, err
+					}
+					B := bf.Var(encodedB)
+					ALO = append(ALO, B)
+					for _, i := range packages {
+						encodedI, err := i.Encode(db)
+						if err != nil {
+							return nil, err
+						}
+						I := bf.Var(encodedI)
+						if !o.Matches(i) {
+							formulas = append(formulas, bf.Or(bf.Not(A), bf.Or(bf.Not(I), bf.Not(B))))
+						}
+					}
+				}
+				formulas = append(formulas, bf.Or(bf.Not(A), bf.Or(ALO...))) // ALO - At least one
+				continue
 			}
+
 		}
 
 		encodedB, err := required.Encode(db)
diff --git a/pkg/solver/solver.go b/pkg/solver/solver.go
index b6948ee3..f6012fae 100644
--- a/pkg/solver/solver.go
+++ b/pkg/solver/solver.go
@@ -28,11 +28,11 @@ import (
 type PackageSolver interface {
 	SetDefinitionDatabase(pkg.PackageDatabase)
 	Install(p []pkg.Package) (PackagesAssertions, error)
-	Uninstall(candidate pkg.Package) ([]pkg.Package, error)
+	Uninstall(candidate pkg.Package, checkconflicts bool) ([]pkg.Package, error)
 	ConflictsWithInstalled(p pkg.Package) (bool, error)
 	ConflictsWith(p pkg.Package, ls []pkg.Package) (bool, error)
 	World() []pkg.Package
-	Upgrade() ([]pkg.Package, PackagesAssertions, error)
+	Upgrade(checkconflicts bool) ([]pkg.Package, PackagesAssertions, error)
 
 	SetResolver(PackageResolver)
 
@@ -210,7 +210,7 @@ func (s *Solver) ConflictsWithInstalled(p pkg.Package) (bool, error) {
 	return s.ConflictsWith(p, s.Installed())
 }
 
-func (s *Solver) Upgrade() ([]pkg.Package, PackagesAssertions, error) {
+func (s *Solver) Upgrade(checkconflicts bool) ([]pkg.Package, PackagesAssertions, error) {
 
 	// First get candidates that needs to be upgraded..
 
@@ -236,12 +236,11 @@ func (s *Solver) Upgrade() ([]pkg.Package, PackagesAssertions, error) {
 			}
 		}
 	}
-
 	s2 := NewSolver(installedcopy, s.DefinitionDatabase, pkg.NewInMemoryDatabase(false))
 	s2.SetResolver(s.Resolver)
 	// Then try to uninstall the versions in the system, and store that tree
 	for _, p := range toUninstall {
-		r, err := s.Uninstall(p)
+		r, err := s.Uninstall(p, checkconflicts)
 		if err != nil {
 			return nil, nil, errors.Wrap(err, "Could not compute upgrade - couldn't uninstall selected candidate "+p.GetFingerPrint())
 		}
@@ -262,7 +261,7 @@ func (s *Solver) Upgrade() ([]pkg.Package, PackagesAssertions, error) {
 
 // Uninstall takes a candidate package and return a list of packages that would be removed
 // in order to purge the candidate. Returns error if unsat.
-func (s *Solver) Uninstall(c pkg.Package) ([]pkg.Package, error) {
+func (s *Solver) Uninstall(c pkg.Package, checkconflicts bool) ([]pkg.Package, error) {
 	var res []pkg.Package
 	candidate, err := s.InstalledDatabase.FindPackage(c)
 	if err != nil {
@@ -294,17 +293,19 @@ func (s *Solver) Uninstall(c pkg.Package) ([]pkg.Package, error) {
 		}
 	}
 
+	s2 := NewSolver(pkg.NewInMemoryDatabase(false), s.DefinitionDatabase, pkg.NewInMemoryDatabase(false))
+	s2.SetResolver(s.Resolver)
 	// Get the requirements to install the candidate
-	saved := s.InstalledDatabase
-	s.InstalledDatabase = pkg.NewInMemoryDatabase(false)
-	asserts, err := s.Install([]pkg.Package{candidate})
+	asserts, err := s2.Install([]pkg.Package{candidate})
 	if err != nil {
 		return nil, err
 	}
-	s.InstalledDatabase = saved
-
 	for _, a := range asserts {
 		if a.Value {
+			if !checkconflicts {
+				res = append(res, a.Package.IsFlagged(false))
+				continue
+			}
 
 			c, err := s.ConflictsWithInstalled(a.Package)
 			if err != nil {
diff --git a/pkg/solver/solver_test.go b/pkg/solver/solver_test.go
index 1609ad83..a751f4bf 100644
--- a/pkg/solver/solver_test.go
+++ b/pkg/solver/solver_test.go
@@ -429,7 +429,7 @@ var _ = Describe("Solver", func() {
 			Expect(solution).To(ContainElement(PackageAssert{Package: D1, Value: false}))
 			Expect(solution).ToNot(ContainElement(PackageAssert{Package: E, Value: true}))
 
-			Expect(len(solution)).To(Equal(5))
+			Expect(len(solution)).To(Equal(6))
 			Expect(err).ToNot(HaveOccurred())
 		})
 
@@ -470,7 +470,7 @@ var _ = Describe("Solver", func() {
 			Expect(solution).To(ContainElement(PackageAssert{Package: D1, Value: false}))
 			Expect(solution).ToNot(ContainElement(PackageAssert{Package: E, Value: true}))
 
-			Expect(len(solution)).To(Equal(4))
+			Expect(len(solution)).To(Equal(6))
 			Expect(err).ToNot(HaveOccurred())
 		})
 
@@ -511,7 +511,7 @@ var _ = Describe("Solver", func() {
 			Expect(solution).To(ContainElement(PackageAssert{Package: D1, Value: false}))
 			Expect(solution).ToNot(ContainElement(PackageAssert{Package: E, Value: true}))
 
-			Expect(len(solution)).To(Equal(4))
+			Expect(len(solution)).To(Equal(6))
 			Expect(err).ToNot(HaveOccurred())
 		})
 
@@ -533,7 +533,7 @@ var _ = Describe("Solver", func() {
 			}
 			s = NewSolver(dbInstalled, dbDefinitions, db)
 
-			solution, err := s.Uninstall(A)
+			solution, err := s.Uninstall(A, true)
 			Expect(err).ToNot(HaveOccurred())
 
 			Expect(solution).To(ContainElement(A.IsFlagged(false)))
@@ -559,7 +559,7 @@ var _ = Describe("Solver", func() {
 			}
 			s = NewSolver(dbInstalled, dbDefinitions, db)
 
-			solution, err := s.Uninstall(&pkg.DefaultPackage{Name: "A", Version: ">1.0"})
+			solution, err := s.Uninstall(&pkg.DefaultPackage{Name: "A", Version: ">1.0"}, true)
 			Expect(err).ToNot(HaveOccurred())
 
 			Expect(solution).To(ContainElement(A.IsFlagged(false)))
@@ -674,7 +674,7 @@ var _ = Describe("Solver", func() {
 				_, err := dbInstalled.CreatePackage(p)
 				Expect(err).ToNot(HaveOccurred())
 			}
-			solution, err := s.Uninstall(A)
+			solution, err := s.Uninstall(A, true)
 			Expect(err).ToNot(HaveOccurred())
 
 			Expect(solution).To(ContainElement(A.IsFlagged(false)))
@@ -698,7 +698,7 @@ var _ = Describe("Solver", func() {
 				_, err := dbInstalled.CreatePackage(p)
 				Expect(err).ToNot(HaveOccurred())
 			}
-			solution, err := s.Uninstall(A)
+			solution, err := s.Uninstall(A, true)
 			Expect(err).ToNot(HaveOccurred())
 
 			Expect(solution).To(ContainElement(A.IsFlagged(false)))
@@ -721,7 +721,7 @@ var _ = Describe("Solver", func() {
 				_, err := dbInstalled.CreatePackage(p)
 				Expect(err).ToNot(HaveOccurred())
 			}
-			solution, err := s.Uninstall(A)
+			solution, err := s.Uninstall(A, true)
 			Expect(err).ToNot(HaveOccurred())
 
 			Expect(solution).To(ContainElement(A.IsFlagged(false)))
@@ -746,7 +746,7 @@ var _ = Describe("Solver", func() {
 				Expect(err).ToNot(HaveOccurred())
 			}
 
-			solution, err := s.Uninstall(A)
+			solution, err := s.Uninstall(A, true)
 			Expect(err).ToNot(HaveOccurred())
 
 			Expect(solution).To(ContainElement(A.IsFlagged(false)))
@@ -772,7 +772,7 @@ var _ = Describe("Solver", func() {
 				Expect(err).ToNot(HaveOccurred())
 			}
 
-			solution, err := s.Uninstall(A)
+			solution, err := s.Uninstall(A, true)
 			Expect(err).ToNot(HaveOccurred())
 
 			Expect(solution).To(ContainElement(A.IsFlagged(false)))
@@ -893,7 +893,7 @@ var _ = Describe("Solver", func() {
 				_, err := dbInstalled.CreatePackage(p)
 				Expect(err).ToNot(HaveOccurred())
 			}
-			uninstall, solution, err := s.Upgrade()
+			uninstall, solution, err := s.Upgrade(true)
 			Expect(err).ToNot(HaveOccurred())
 
 			Expect(len(uninstall)).To(Equal(1))
diff --git a/tests/fixtures/upgrade_integration/c/definition.yaml b/tests/fixtures/upgrade_integration/c/definition.yaml
index 348454f7..e63d83a3 100644
--- a/tests/fixtures/upgrade_integration/c/definition.yaml
+++ b/tests/fixtures/upgrade_integration/c/definition.yaml
@@ -1,3 +1,9 @@
 category: "test"
 name: "c"
 version: "1.0"
+# Boom?
+
+requires:
+- category: "test"
+  name: "a"
+  version: ">=0.1"
\ No newline at end of file
diff --git a/tests/fixtures/upgrade_integration/cat/a/alatest/build.yaml b/tests/fixtures/upgrade_integration/cat/a/alatest/build.yaml
new file mode 100644
index 00000000..496c04ca
--- /dev/null
+++ b/tests/fixtures/upgrade_integration/cat/a/alatest/build.yaml
@@ -0,0 +1,11 @@
+image: "alpine"
+prelude:
+  - echo foo > /test
+  - echo bar > /test2
+steps:
+  - echo artifact3 > /testlatest
+  - echo artifact4 > /testlatest2
+requires:
+- category: "test"
+  name: "b"
+  version: "1.0"
diff --git a/tests/fixtures/upgrade_integration/cat/a/alatest/definition.yaml b/tests/fixtures/upgrade_integration/cat/a/alatest/definition.yaml
new file mode 100644
index 00000000..006dd943
--- /dev/null
+++ b/tests/fixtures/upgrade_integration/cat/a/alatest/definition.yaml
@@ -0,0 +1,3 @@
+category: "test"
+name: "a"
+version: "1.2"
diff --git a/tests/integration/03_qlearning.sh b/tests/integration/03_qlearning.sh
index 0cad6b73..d8c8c03a 100755
--- a/tests/integration/03_qlearning.sh
+++ b/tests/integration/03_qlearning.sh
@@ -12,7 +12,7 @@ oneTimeTearDown() {
 
 testBuild() {
     mkdir $tmpdir/testbuild
-    luet build --all --tree "$ROOT_DIR/tests/fixtures/qlearning" --destination $tmpdir/testbuild --compression gzip
+    luet build --all --concurrency 1 --tree "$ROOT_DIR/tests/fixtures/qlearning" --destination $tmpdir/testbuild --compression gzip
     buildst=$?
     assertEquals 'builds successfully' "$buildst" "0"
     assertTrue 'create package dep B' "[ -e '$tmpdir/testbuild/b-test-1.0.package.tar.gz' ]"
diff --git a/tests/integration/05_upgrade.sh b/tests/integration/05_upgrade.sh
index 50d43b33..ac86c582 100755
--- a/tests/integration/05_upgrade.sh
+++ b/tests/integration/05_upgrade.sh
@@ -29,10 +29,22 @@ testBuild() {
 
     luet build --tree "$ROOT_DIR/tests/fixtures/upgrade_integration" --destination $tmpdir/testbuild --compression gzip test/a-1.1
     buildst=$?
-        assertEquals 'builds successfully' "$buildst" "0"
+    assertEquals 'builds successfully' "$buildst" "0"
 
     assertTrue 'create package A 1.1' "[ -e '$tmpdir/testbuild/a-test-1.1.package.tar.gz' ]"
 
+    luet build --tree "$ROOT_DIR/tests/fixtures/upgrade_integration" --destination $tmpdir/testbuild --compression gzip test/a-1.2
+    buildst=$?
+    assertEquals 'builds successfully' "$buildst" "0"
+
+    assertTrue 'create package A 1.2' "[ -e '$tmpdir/testbuild/a-test-1.2.package.tar.gz' ]"
+
+
+    luet build --tree "$ROOT_DIR/tests/fixtures/upgrade_integration" --destination $tmpdir/testbuild --compression gzip test/c-1.0
+    buildst=$?
+    assertEquals 'builds successfully' "$buildst" "0"
+    assertTrue 'create package C 1.0' "[ -e '$tmpdir/testbuild/c-test-1.0.package.tar.gz' ]"
+
 }
 
 testRepo() {
@@ -73,27 +85,36 @@ EOF
 
 testInstall() {
     luet install --config $tmpdir/luet.yaml test/b-1.0
-    #luet install --config $tmpdir/luet.yaml test/c-1.0 > /dev/null
     installst=$?
     assertEquals 'install test successfully' "$installst" "0"
     assertTrue 'package installed B' "[ -e '$tmpdir/testrootfs/test5' ]"
 
     luet install --config $tmpdir/luet.yaml test/a-1.0
-    #luet install --config $tmpdir/luet.yaml test/c-1.0 > /dev/null
-        assertTrue 'package installed A' "[ -e '$tmpdir/testrootfs/testaa' ]"
-
+    assertTrue 'package installed A' "[ -e '$tmpdir/testrootfs/testaa' ]"
     installst=$?
+    assertEquals 'install test successfully' "$installst" "0"
+
+    luet install --config $tmpdir/luet.yaml test/a-1.1
+    assertTrue 'package installed A' "[ -e '$tmpdir/testrootfs/testaa' ]"
+    installst=$?
+    assertEquals 'install test successfully' "$installst" "0"
+    assertTrue 'package keeps old A' "[ -e '$tmpdir/testrootfs/testaa' ]"
+    assertTrue 'package new A was not installed' "[ ! -e '$tmpdir/testrootfs/testlatest' ]"
+
+    luet install --config $tmpdir/luet.yaml test/c-1.0
+    installst=$?
+    assertEquals 'install test successfully' "$installst" "0"
+    assertTrue 'package installed C' "[ -e '$tmpdir/testrootfs/c' ]"
 }
 
 testUpgrade() {
-    output=$(luet --config $tmpdir/luet.yaml upgrade)
+    luet --config $tmpdir/luet.yaml upgrade
     installst=$?
-    echo $output
     assertEquals 'install test successfully' "$installst" "0"
     assertTrue 'package uninstalled B' "[ ! -e '$tmpdir/testrootfs/test5' ]"
     assertTrue 'package installed B' "[ -e '$tmpdir/testrootfs/newc' ]"
     assertTrue 'package uninstalled A' "[ ! -e '$tmpdir/testrootfs/testaa' ]"
-    assertTrue 'package installed new A' "[ -e '$tmpdir/testrootfs/test3' ]"
+    assertTrue 'package installed new A' "[ -e '$tmpdir/testrootfs/testlatest' ]"
 }
 
 # Load shUnit2.