diff --git a/platform/vcs-log/graph/src/com/intellij/vcs/log/graph/collapsing/CollapsedActionManager.java b/platform/vcs-log/graph/src/com/intellij/vcs/log/graph/collapsing/CollapsedActionManager.java
index de07de3b2465..0de15a9eaea1 100644
--- a/platform/vcs-log/graph/src/com/intellij/vcs/log/graph/collapsing/CollapsedActionManager.java
+++ b/platform/vcs-log/graph/src/com/intellij/vcs/log/graph/collapsing/CollapsedActionManager.java
@@ -197,9 +197,8 @@ final class CollapsedActionManager {
   };
 
   private final static ActionCase EXPAND_ALL = new ActionCase() {
-    @Nullable
     @Override
-    public LinearGraphAnswer performAction(@NotNull ActionContext context) {
+    public @NotNull LinearGraphAnswer performAction(@NotNull ActionContext context) {
       CollapsedGraph.Modification modification = context.myCollapsedGraph.startModification();
       modification.removeAdditionalEdges();
       modification.resetNodesVisibility();
@@ -214,9 +213,8 @@ final class CollapsedActionManager {
   };
 
   private final static ActionCase COLLAPSE_ALL = new ActionCase() {
-    @Nullable
     @Override
-    public LinearGraphAnswer performAction(@NotNull ActionContext context) {
+    public @NotNull LinearGraphAnswer performAction(@NotNull ActionContext context) {
       CollapsedGraph.Modification modification = context.myCollapsedGraph.startModification();
       modification.removeAdditionalEdges();
       modification.resetNodesVisibility();
diff --git a/platform/vcs-log/graph/src/com/intellij/vcs/log/graph/linearBek/LinearBekController.java b/platform/vcs-log/graph/src/com/intellij/vcs/log/graph/linearBek/LinearBekController.java
index 72cb80797844..251cd9fddf15 100644
--- a/platform/vcs-log/graph/src/com/intellij/vcs/log/graph/linearBek/LinearBekController.java
+++ b/platform/vcs-log/graph/src/com/intellij/vcs/log/graph/linearBek/LinearBekController.java
@@ -96,9 +96,8 @@ public class LinearBekController extends CascadeController {
   @NotNull
   private LinearGraphAnswer expandAll() {
     return new LinearGraphAnswer(GraphChangesUtil.SOME_CHANGES) {
-      @Nullable
       @Override
-      public Runnable getGraphUpdater() {
+      public @NotNull Runnable getGraphUpdater() {
         return () -> {
           myCompiledGraph.myDottedEdges.removeAll();
           myCompiledGraph.myHiddenEdges.removeAll();
@@ -113,9 +112,8 @@ public class LinearBekController extends CascadeController {
     new LinearBekGraphBuilder(workingGraph, myBekGraphLayout).collapseAll();
     return new LinearGraphAnswer(
       GraphChangesUtil.edgesReplaced(workingGraph.getRemovedEdges(), workingGraph.getAddedEdges(), getDelegateGraph())) {
-      @Nullable
       @Override
-      public Runnable getGraphUpdater() {
+      public @NotNull Runnable getGraphUpdater() {
         return () -> workingGraph.applyChanges();
       }
     };
diff --git a/plugins/git4idea/src/git4idea/history/GitHistoryProvider.java b/plugins/git4idea/src/git4idea/history/GitHistoryProvider.java
index 69b0d9aa4b44..9ca7879303f5 100644
--- a/plugins/git4idea/src/git4idea/history/GitHistoryProvider.java
+++ b/plugins/git4idea/src/git4idea/history/GitHistoryProvider.java
@@ -84,8 +84,7 @@ public final class GitHistoryProvider implements VcsHistoryProviderEx,
   }
 
   @Override
-  @Nullable
-  public VcsAbstractHistorySession createSessionFor(final FilePath filePath) throws VcsException {
+  public @NotNull VcsAbstractHistorySession createSessionFor(final FilePath filePath) throws VcsException {
     List<VcsFileRevision> revisions = GitFileHistory.collectHistory(myProject, filePath);
     return createSession(filePath, revisions, revisions.isEmpty() ? null : getFirstItem(revisions).getRevisionNumber());
   }