diff --git a/java/java-tests/testData/codeInsight/completion/normalSorting/DispreferUnderscoredCaseMatch.java b/java/java-tests/testData/codeInsight/completion/normalSorting/DispreferUnderscoredCaseMatch.java
new file mode 100644
index 000000000000..21ba4e5aa742
--- /dev/null
+++ b/java/java-tests/testData/codeInsight/completion/normalSorting/DispreferUnderscoredCaseMatch.java
@@ -0,0 +1,5 @@
+class Zoo {
+  void zoo(String fooBar, String __foo_bar) {
+    foo<caret>
+  }
+}
\ No newline at end of file
diff --git a/java/java-tests/testSrc/com/intellij/java/codeInsight/completion/NormalCompletionOrderingTest.groovy b/java/java-tests/testSrc/com/intellij/java/codeInsight/completion/NormalCompletionOrderingTest.groovy
index 46257504acf2..f44f25fd1adf 100644
--- a/java/java-tests/testSrc/com/intellij/java/codeInsight/completion/NormalCompletionOrderingTest.groovy
+++ b/java/java-tests/testSrc/com/intellij/java/codeInsight/completion/NormalCompletionOrderingTest.groovy
@@ -443,6 +443,10 @@ interface TxANotAnno {}
     checkPreferredItems(0, 'fooBar', '_fooBar', 'FooBar')
   }
 
+  void testDispreferUnderscoredCaseMatch() {
+    checkPreferredItems(0, 'fooBar', '__foo_bar')
+  }
+
   void testStatisticsMattersOnNextCompletion() {
     configureByFile(getTestName(false) + ".java")
     myFixture.completeBasic()
diff --git a/platform/lang-impl/src/com/intellij/codeInsight/completion/impl/CamelHumpMatcher.java b/platform/lang-impl/src/com/intellij/codeInsight/completion/impl/CamelHumpMatcher.java
index 73923b6e395c..9fc55743281d 100644
--- a/platform/lang-impl/src/com/intellij/codeInsight/completion/impl/CamelHumpMatcher.java
+++ b/platform/lang-impl/src/com/intellij/codeInsight/completion/impl/CamelHumpMatcher.java
@@ -63,14 +63,26 @@ public class CamelHumpMatcher extends PrefixMatcher {
   @Override
   public boolean prefixMatches(@NotNull final String name) {
     if (name.startsWith("_") &&
-        myPrefix.length() > 0 && Character.isLetter(myPrefix.charAt(0)) &&
-        CodeInsightSettings.getInstance().COMPLETION_CASE_SENSITIVE == CodeInsightSettings.FIRST_LETTER) {
+        CodeInsightSettings.getInstance().COMPLETION_CASE_SENSITIVE == CodeInsightSettings.FIRST_LETTER &&
+        firstLetterCaseDiffers(name)) {
       return false;
     }
 
     return myMatcher.matches(name);
   }
 
+  private boolean firstLetterCaseDiffers(String name) {
+    int nameFirst = skipUnderscores(name);
+    int prefixFirst = skipUnderscores(myPrefix);
+    return nameFirst < name.length() &&
+           prefixFirst < myPrefix.length() &&
+           caseDiffers(name.charAt(nameFirst), myPrefix.charAt(prefixFirst));
+  }
+
+  private static boolean caseDiffers(char c1, char c2) {
+    return Character.isLowerCase(c1) != Character.isLowerCase(c2) || Character.isUpperCase(c1) != Character.isUpperCase(c2);
+  }
+
   @Override
   public boolean prefixMatches(@NotNull final LookupElement element) {
     return prefixMatchersInternal(element, !element.isCaseSensitive());
diff --git a/python/testSrc/com/jetbrains/python/PythonCompletionTest.java b/python/testSrc/com/jetbrains/python/PythonCompletionTest.java
index b99354a514ba..39f3698a7e89 100644
--- a/python/testSrc/com/jetbrains/python/PythonCompletionTest.java
+++ b/python/testSrc/com/jetbrains/python/PythonCompletionTest.java
@@ -23,6 +23,7 @@ import com.intellij.codeInsight.lookup.Lookup;
 import com.intellij.codeInsight.lookup.LookupElement;
 import com.intellij.codeInsight.lookup.LookupElementBuilder;
 import com.intellij.testFramework.PsiTestUtil;
+import com.jetbrains.python.documentation.PyDocumentationSettings;
 import com.jetbrains.python.documentation.docstrings.DocStringFormat;
 import com.jetbrains.python.fixtures.PyTestCase;
 import com.jetbrains.python.psi.LanguageLevel;
@@ -1067,7 +1068,7 @@ public class PythonCompletionTest extends PyTestCase {
                                                 "@six.add_metaclass(M)\n" +
                                                 "class C(object):\n" +
                                                 "    def foo(self):\n" +
-                                                "        C.ba<caret>x()");
+                                                "        C.ba<caret>()");
 
     assertNotNull(suggested);
     assertContainsElements(suggested, "baz");
@@ -1081,7 +1082,7 @@ public class PythonCompletionTest extends PyTestCase {
                                                 "@a_m(M)\n" +
                                                 "class C(object):\n" +
                                                 "    def foo(self):\n" +
-                                                "        C.ba<caret>x()");
+                                                "        C.ba<caret>()");
 
     assertNotNull(suggested);
     assertContainsElements(suggested, "baz");