diff --git a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/DfaMemoryStateImpl.java b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/DfaMemoryStateImpl.java
index 30eae15890a5..1634815041ce 100644
--- a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/DfaMemoryStateImpl.java
+++ b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/DfaMemoryStateImpl.java
@@ -255,7 +255,7 @@ public class DfaMemoryStateImpl implements DfaMemoryState {
 
     setVariableState(var, getVariableState(var).withValue(value));
     if (value instanceof DfaTypeValue) {
-      setVariableState(var, getVariableState(var).withNullable(((DfaTypeValue)value).isNullable()));
+      setVariableState(var, getVariableState(var).withNullability(((DfaTypeValue)value).getNullness()));
       DfaRelationValue dfaInstanceof = myFactory.getRelationFactory().createRelation(var, value, JavaTokenType.INSTANCEOF_KEYWORD, false);
       if (((DfaTypeValue)value).isNotNull()) {
         applyCondition(dfaInstanceof);
diff --git a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/StandardInstructionVisitor.java b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/StandardInstructionVisitor.java
index ed52d2c5e78b..126c48ff5fc5 100644
--- a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/StandardInstructionVisitor.java
+++ b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/StandardInstructionVisitor.java
@@ -66,10 +66,11 @@ public class StandardInstructionVisitor extends InstructionVisitor {
     if (dfaDest instanceof DfaVariableValue) {
       DfaVariableValue var = (DfaVariableValue) dfaDest;
 
-      if (var.getInherentNullability() == Nullness.NOT_NULL) {
+      final PsiModifierListOwner psi = var.getPsiVariable();
+      boolean forceDeclaredNullity = !(psi instanceof PsiParameter && psi.getParent() instanceof PsiParameterList);
+      if (forceDeclaredNullity && var.getInherentNullability() == Nullness.NOT_NULL) {
         checkNotNullable(memState, dfaSource, NullabilityProblem.assigningToNotNull, instruction.getRExpression());
       }
-      final PsiModifierListOwner psi = var.getPsiVariable();
       if (!(psi instanceof PsiField) || !psi.hasModifierProperty(PsiModifier.VOLATILE)) {
         memState.setVarValue(var, dfaSource);
       }
diff --git a/java/java-tests/testData/inspection/dataFlow/NotNullLocalVariable/expected.xml b/java/java-tests/testData/inspection/dataFlow/NotNullLocalVariable/expected.xml
index 0661e23a2761..580a889dbfd6 100644
--- a/java/java-tests/testData/inspection/dataFlow/NotNullLocalVariable/expected.xml
+++ b/java/java-tests/testData/inspection/dataFlow/NotNullLocalVariable/expected.xml
@@ -1,8 +1,3 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <problems>
-  <problem>
-    <file>Npe.java</file>
-    <line>7</line>
-    <description>Condition 'o == null' is always false</description>
-  </problem>
 </problems>
diff --git a/java/java-tests/testData/inspection/dataFlow/fixture/MethodParametersCanChangeNullability.java b/java/java-tests/testData/inspection/dataFlow/fixture/MethodParametersCanChangeNullability.java
new file mode 100644
index 000000000000..b54637a15225
--- /dev/null
+++ b/java/java-tests/testData/inspection/dataFlow/fixture/MethodParametersCanChangeNullability.java
@@ -0,0 +1,33 @@
+import org.jetbrains.annotations.*;
+
+class Test {
+
+  @Nullable
+  String findMessage(@NotNull Element element) {
+    while (element != null) {
+      if (element.getMessage() != null) {
+        return element.getMessage();
+      }
+      element = element.getParent();
+    }
+    return null;
+  }
+
+  @Nullable
+  String findMessageWithNullableParent(@NotNull Element element) {
+    while (element != null) {
+      if (element.getMessage() != null) {
+        return element.getMessage();
+      }
+      element = element.getNullableParent();
+    }
+    return null;
+  }
+
+}
+
+interface Element {
+  Element getParent();
+  @Nullable Element getNullableParent();
+  @Nullable String getMessage();
+}
\ No newline at end of file
diff --git a/java/java-tests/testSrc/com/intellij/codeInspection/DataFlowInspectionTest.java b/java/java-tests/testSrc/com/intellij/codeInspection/DataFlowInspectionTest.java
index f502baa392f5..d79d3fca6a90 100644
--- a/java/java-tests/testSrc/com/intellij/codeInspection/DataFlowInspectionTest.java
+++ b/java/java-tests/testSrc/com/intellij/codeInspection/DataFlowInspectionTest.java
@@ -301,6 +301,8 @@ public class DataFlowInspectionTest extends DataFlowInspectionTestCase {
 
   public void testAccessingSameArrayElements() { doTest(); }
 
+  public void testMethodParametersCanChangeNullability() { doTest(); }
+
   public void testParametersAreNonnullByDefault() {
     addJavaxNullabilityAnnotations(myFixture);
     addJavaxDefaultNullabilityAnnotations(myFixture);