diff --git a/third_party/src/main/java/com/jetbrains/lang/dart/assists/DartQuickAssistIntention.java b/third_party/src/main/java/com/jetbrains/lang/dart/assists/DartQuickAssistIntention.java
index ff338d2be..5e5fd2434 100644
--- a/third_party/src/main/java/com/jetbrains/lang/dart/assists/DartQuickAssistIntention.java
+++ b/third_party/src/main/java/com/jetbrains/lang/dart/assists/DartQuickAssistIntention.java
@@ -30,7 +30,7 @@ public DartQuickAssistIntention(int index) {
   }
 
   @Override
-  public int compareTo(IntentionAction o) {
+  public int compareTo(final @NotNull IntentionAction o) {
     if (o instanceof DartQuickAssistIntention other) {
       return myIndex - other.myIndex;
     }
diff --git a/third_party/src/main/java/com/jetbrains/lang/dart/fixes/DartQuickFix.java b/third_party/src/main/java/com/jetbrains/lang/dart/fixes/DartQuickFix.java
index 9f2f78a39..ac509628e 100644
--- a/third_party/src/main/java/com/jetbrains/lang/dart/fixes/DartQuickFix.java
+++ b/third_party/src/main/java/com/jetbrains/lang/dart/fixes/DartQuickFix.java
@@ -65,7 +65,7 @@ public DartQuickFix(final @NotNull DartQuickFixSet quickFixSet, final int index)
   }
 
   @Override
-  public int compareTo(IntentionAction o) {
+  public int compareTo(final @NotNull IntentionAction o) {
     if (o instanceof DartQuickFix) {
       return myIndex - ((DartQuickFix)o).myIndex;
     }
diff --git a/third_party/src/main/java/com/jetbrains/lang/dart/ide/annotator/DartProblemGroup.java b/third_party/src/main/java/com/jetbrains/lang/dart/ide/annotator/DartProblemGroup.java
index b0538879e..3cfc9c8ac 100644
--- a/third_party/src/main/java/com/jetbrains/lang/dart/ide/annotator/DartProblemGroup.java
+++ b/third_party/src/main/java/com/jetbrains/lang/dart/ide/annotator/DartProblemGroup.java
@@ -134,7 +134,7 @@ public DartSuppressAction(@NotNull String errorCode, boolean eolComment) {
     }
 
     @Override
-    public int compareTo(final IntentionAction o) {
+    public int compareTo(final @NotNull IntentionAction o) {
       if (o instanceof DartSuppressAction) {
         return ((DartSuppressAction)o).myEolComment ? -1 : 1;
       }
diff --git a/third_party/src/main/java/com/jetbrains/lang/dart/ide/runner/test/DartTestEventsConverter.java b/third_party/src/main/java/com/jetbrains/lang/dart/ide/runner/test/DartTestEventsConverter.java
index 273e61fea..462137e3c 100644
--- a/third_party/src/main/java/com/jetbrains/lang/dart/ide/runner/test/DartTestEventsConverter.java
+++ b/third_party/src/main/java/com/jetbrains/lang/dart/ide/runner/test/DartTestEventsConverter.java
@@ -106,7 +106,7 @@ public DartTestEventsConverter(final @NotNull String testFrameworkName,
   }
 
   @Override
-  protected boolean processServiceMessages(final String text, final Key outputType, final ServiceMessageVisitor visitor)
+  protected boolean processServiceMessages(final String text, final @NotNull Key outputType, final @NotNull ServiceMessageVisitor visitor)
     throws ParseException {
     LOG.debug("<<< " + text.trim());
     myCurrentOutputType = outputType;
diff --git a/third_party/src/main/java/com/jetbrains/lang/dart/pubServer/PubServerManager.java b/third_party/src/main/java/com/jetbrains/lang/dart/pubServer/PubServerManager.java
index 719a34f1b..27fc808fb 100644
--- a/third_party/src/main/java/com/jetbrains/lang/dart/pubServer/PubServerManager.java
+++ b/third_party/src/main/java/com/jetbrains/lang/dart/pubServer/PubServerManager.java
@@ -32,7 +32,7 @@ public final class PubServerManager implements Disposable {
 
   private String myServedSdkVersion;
 
-  private final LoadingCache<VirtualFile, PubServerService> myServedDirToPubService;
+  private final LoadingCache<@NotNull VirtualFile, PubServerService> myServedDirToPubService;
 
   public static @NotNull PubServerManager getInstance(@NotNull Project project) {
     return project.getService(PubServerManager.class);