diff --git a/sdk/lib/_internal/pub/lib/src/solver/backtracking_solver.dart b/sdk/lib/_internal/pub/lib/src/solver/backtracking_solver.dart
index 69230e7..efb6fba 100644
--- a/sdk/lib/_internal/pub/lib/src/solver/backtracking_solver.dart
+++ b/sdk/lib/_internal/pub/lib/src/solver/backtracking_solver.dart
@@ -192,29 +192,7 @@
     var dependers = failure.dependencies.map((dep) => dep.depender).toSet();
 
     while (!_selected.isEmpty) {
-      // Look for a relevant selection to jump back to.
-      for (var i = _selected.length - 1; i >= 0; i--) {
-        // Can't jump to a package that has no more alternatives.
-        if (_selected[i].length == 1) continue;
-
-        var selected = _selected[i].first;
-
-        // If we find the package itself that failed, jump to it.
-        if (selected.name == failure.package) {
-          logSolve('jump to selected package ${failure.package}');
-          _selected.removeRange(i + 1, _selected.length);
-          break;
-        }
-
-        // See if this package directly or indirectly depends on [package].
-        var path = _getDependencyPath(selected, failure.package);
-        if (path != null) {
-          logSolve('backjump to ${selected.name} because it depends on '
-                   '${failure.package}  by $path');
-          _selected.removeRange(i + 1, _selected.length);
-          break;
-        }
-      }
+      _backjump(failure);
 
       // Advance past the current version of the leaf-most package.
       var previous = _selected.last.removeFirst();
@@ -232,6 +210,44 @@
     return false;
   }
 
+  /// Walks the selected packages from most to least recent to determine which
+  /// ones can be ignored and jumped over by the backtracker. The only packages
+  /// we need to backtrack to are ones that have other versions to try and that
+  /// led (possibly indirectly) to the failure. Everything else can be skipped.
+  void _backjump(SolveFailure failure) {
+    for (var i = _selected.length - 1; i >= 0; i--) {
+      // Each queue will never be empty since it gets discarded by _backtrack()
+      // when that happens.
+      var selected = _selected[i].first;
+
+      // If the package has no more versions, we can jump over it.
+      if (_selected[i].length == 1) continue;
+
+      // If we get to the package that failed, backtrack to here.
+      if (selected.name == failure.package) {
+        logSolve('backjump to failed package ${selected.name}');
+        _selected.removeRange(i + 1, _selected.length);
+        return;
+      }
+
+      // If we get to a package that depends on the failing package, backtrack
+      // to here.
+      var path = _getDependencyPath(selected, failure.package);
+      if (path != null) {
+        logSolve('backjump to ${selected.name} because it depends on '
+                 '${failure.package} along $path');
+        _selected.removeRange(i + 1, _selected.length);
+        return;
+      }
+    }
+
+    // If we got here, we walked the entire list without finding a package that
+    // could lead to another solution, so discard everything. This will happen
+    // if every package that led to the failure has no other versions that it
+    // can try to select.
+    _selected.removeRange(1, _selected.length);
+  }
+
   /// Determines if [depender] has a direct or indirect dependency on
   /// [dependent] based on the currently selected versions of all packages.
   /// Returns a string describing the dependency chain if it does, or `null` if
@@ -592,7 +608,7 @@
 
   if (pubspec.environment.sdkVersion.allows(sdk.version)) return;
 
-  throw new CouldNotSolveException(
+  throw new BadSdkVersionException(pubspec.name,
       'Package ${pubspec.name} requires SDK version '
       '${pubspec.environment.sdkVersion} but the current SDK is '
       '${sdk.version}.');
diff --git a/sdk/lib/_internal/pub/lib/src/solver/version_solver.dart b/sdk/lib/_internal/pub/lib/src/solver/version_solver.dart
index efd9e85..885acdc 100644
--- a/sdk/lib/_internal/pub/lib/src/solver/version_solver.dart
+++ b/sdk/lib/_internal/pub/lib/src/solver/version_solver.dart
@@ -218,13 +218,12 @@
       "depends on version ${dep.constraint}";
 }
 
-/// Exception thrown when the [VersionSolver] fails to find a solution after a
-/// certain number of iterations.
-class CouldNotSolveException extends SolveFailure {
-  CouldNotSolveException([String message])
-      : super(null, null),
-        _message = (message != null) ? message :
-            "Could not find a solution that met all constraints.";
+/// Exception thrown when the current SDK's version does not match a package's
+/// constraint on it.
+class BadSdkVersionException extends SolveFailure {
+  BadSdkVersionException(String package, String message)
+      : super(package, null),
+        _message = message;
 
   /// A message describing the specific kind of solve failure.
   final String _message;
diff --git a/sdk/lib/_internal/pub/test/version_solver_test.dart b/sdk/lib/_internal/pub/test/version_solver_test.dart
index 6c2cb22..35af3ac 100644
--- a/sdk/lib/_internal/pub/test/version_solver_test.dart
+++ b/sdk/lib/_internal/pub/test/version_solver_test.dart
@@ -10,6 +10,7 @@
 import 'package:unittest/unittest.dart';
 
 import '../lib/src/lock_file.dart';
+import '../lib/src/log.dart' as log;
 import '../lib/src/package.dart';
 import '../lib/src/pubspec.dart';
 import '../lib/src/sdk.dart' as sdk;
@@ -27,6 +28,9 @@
 main() {
   initConfig();
 
+  // Uncomment this to debug failing tests.
+  // log.showSolver();
+
   // Since this test isn't run from the SDK, it can't find the "version" file
   // to load. Instead, just manually inject a version.
   sdk.version = new Version(1, 2, 3);
@@ -484,6 +488,111 @@
     'c': '1.0.0'
   }, maxTries: 2);
 
+  // Tests that the backjumper will jump past unrelated selections when a
+  // source conflict occurs. This test selects, in order:
+  // - myapp -> a
+  // - myapp -> b
+  // - myapp -> c (1 of 5)
+  // - b -> a
+  // It selects a and b first because they have fewer versions than c. It
+  // traverses b's dependency on a after selecting a version of c because
+  // dependencies are traversed breadth-first (all of myapps's immediate deps
+  // before any other their deps).
+  //
+  // This means it doesn't discover the source conflict until after selecting
+  // c. When that happens, it should backjump past c instead of trying older
+  // versions of it since they aren't related to the conflict.
+  testResolve('backjump to conflicting source', {
+    'myapp 0.0.0': {
+      'a': 'any',
+      'b': 'any',
+      'c': 'any'
+    },
+    'a 1.0.0': {},
+    'a 1.0.0 from mock2': {},
+    'b 1.0.0': {
+      'a': 'any'
+    },
+    'b 2.0.0': {
+      'a from mock2': 'any'
+    },
+    'c 1.0.0': {},
+    'c 2.0.0': {},
+    'c 3.0.0': {},
+    'c 4.0.0': {},
+    'c 5.0.0': {},
+  }, result: {
+    'myapp from root': '0.0.0',
+    'a': '1.0.0',
+    'b': '1.0.0',
+    'c': '5.0.0'
+  }, maxTries: 2);
+
+  // Like the above test, but for a conflicting description.
+  testResolve('backjump to conflicting description', {
+    'myapp 0.0.0': {
+      'a-x': 'any',
+      'b': 'any',
+      'c': 'any'
+    },
+    'a-x 1.0.0': {},
+    'a-y 1.0.0': {},
+    'b 1.0.0': {
+      'a-x': 'any'
+    },
+    'b 2.0.0': {
+      'a-y': 'any'
+    },
+    'c 1.0.0': {},
+    'c 2.0.0': {},
+    'c 3.0.0': {},
+    'c 4.0.0': {},
+    'c 5.0.0': {},
+  }, result: {
+    'myapp from root': '0.0.0',
+    'a': '1.0.0',
+    'b': '1.0.0',
+    'c': '5.0.0'
+  }, maxTries: 2);
+
+  // Similar to the above two tests but where there is no solution. It should
+  // fail in this case with no backtracking.
+  testResolve('backjump to conflicting source', {
+    'myapp 0.0.0': {
+      'a': 'any',
+      'b': 'any',
+      'c': 'any'
+    },
+    'a 1.0.0': {},
+    'a 1.0.0 from mock2': {},
+    'b 1.0.0': {
+      'a from mock2': 'any'
+    },
+    'c 1.0.0': {},
+    'c 2.0.0': {},
+    'c 3.0.0': {},
+    'c 4.0.0': {},
+    'c 5.0.0': {},
+  }, error: sourceMismatch('myapp', 'b'), maxTries: 1);
+
+  testResolve('backjump to conflicting description', {
+    'myapp 0.0.0': {
+      'a-x': 'any',
+      'b': 'any',
+      'c': 'any'
+    },
+    'a-x 1.0.0': {},
+    'a-y 1.0.0': {},
+    'b 1.0.0': {
+      'a-y': 'any'
+    },
+    'c 1.0.0': {},
+    'c 2.0.0': {},
+    'c 3.0.0': {},
+    'c 4.0.0': {},
+    'c 5.0.0': {},
+  }, error: descriptionMismatch('myapp', 'b'), maxTries: 1);
+
   // Dependencies are ordered so that packages with fewer versions are tried
   // first. Here, there are two valid solutions (either a or b must be
   // downgraded once). The chosen one depends on which dep is traversed first.
@@ -619,13 +728,31 @@
   }, useBleedingEdgeSdkVersion: true);
 }
 
-testResolve(description, packages,
-            {lockfile, result, FailMatcherBuilder error, int maxTries,
+testResolve(description, packages, {
+             lockfile, result, FailMatcherBuilder error, int maxTries,
+             bool useBleedingEdgeSdkVersion}) {
+  _testResolve(test, description, packages, lockfile: lockfile, result: result,
+      error: error, maxTries: maxTries,
+      useBleedingEdgeSdkVersion: useBleedingEdgeSdkVersion);
+}
+
+solo_testResolve(description, packages, {
+             lockfile, result, FailMatcherBuilder error, int maxTries,
+             bool useBleedingEdgeSdkVersion}) {
+  log.showSolver();
+  _testResolve(solo_test, description, packages, lockfile: lockfile,
+      result: result, error: error, maxTries: maxTries,
+      useBleedingEdgeSdkVersion: useBleedingEdgeSdkVersion);
+}
+
+_testResolve(void testFn(String description, Function body),
+             description, packages, {
+             lockfile, result, FailMatcherBuilder error, int maxTries,
              bool useBleedingEdgeSdkVersion}) {
   if (maxTries == null) maxTries = 1;
   if (useBleedingEdgeSdkVersion == null) useBleedingEdgeSdkVersion = false;
 
-  test(description, () {
+  testFn(description, () {
     var cache = new SystemCache('.');
     source1 = new MockSource('mock1');
     source2 = new MockSource('mock2');