diff --git a/RegExpSupport/resources/messages/RegExpBundle.properties b/RegExpSupport/resources/messages/RegExpBundle.properties
index 0465ec66d92d..a7ec83c55e30 100644
--- a/RegExpSupport/resources/messages/RegExpBundle.properties
+++ b/RegExpSupport/resources/messages/RegExpBundle.properties
@@ -31,6 +31,7 @@ error.dangling.opening.bracket=Unexpected start of quantifier '{'
 error.embedded.comments.are.not.supported.in.this.regex.dialect=Embedded comments are not supported in this regex dialect
 error.empty.group=Empty group
 error.group.reference.is.nested.into.the.named.group.it.refers.to=Group reference is nested into the named group it refers to
+error.define.subpattern.contains.more.than.one.branch=DEFINE subpattern contains more than one branch
 error.group.reference.not.allowed.inside.lookbehind=Group reference not allowed inside lookbehind
 error.group.with.name.0.already.defined=Group with name ''{0}'' already defined
 error.illegal.character.range.to.from=Illegal character range (to < from)
diff --git a/RegExpSupport/src/org/intellij/lang/regexp/psi/impl/RegExpGroupImpl.java b/RegExpSupport/src/org/intellij/lang/regexp/psi/impl/RegExpGroupImpl.java
index 407f1fe98ce3..f4c853f35402 100644
--- a/RegExpSupport/src/org/intellij/lang/regexp/psi/impl/RegExpGroupImpl.java
+++ b/RegExpSupport/src/org/intellij/lang/regexp/psi/impl/RegExpGroupImpl.java
@@ -102,6 +102,10 @@ public class RegExpGroupImpl extends RegExpElementImpl implements RegExpGroup {
     return node != null && node.findChildByType(RegExpTT.PCRE_CONDITION) != null;
   }
 
+  public static boolean isPcreDefine(ASTNode node) {
+    return node != null && node.findChildByType(RegExpTT.PCRE_DEFINE) != null;
+  }
+
   @Override
   public String getGroupName() {
     final ASTNode nameNode = getNode().findChildByType(RegExpTT.NAME);
diff --git a/RegExpSupport/src/org/intellij/lang/regexp/validation/RegExpAnnotator.java b/RegExpSupport/src/org/intellij/lang/regexp/validation/RegExpAnnotator.java
index f5e2176ffb96..d8c826815f57 100644
--- a/RegExpSupport/src/org/intellij/lang/regexp/validation/RegExpAnnotator.java
+++ b/RegExpSupport/src/org/intellij/lang/regexp/validation/RegExpAnnotator.java
@@ -29,10 +29,10 @@ import com.intellij.psi.PsiElement;
 import com.intellij.psi.StringEscapesTokenTypes;
 import com.intellij.psi.tree.IElementType;
 import com.intellij.psi.util.PsiTreeUtil;
+import com.intellij.util.ObjectUtils;
 import com.intellij.util.containers.ContainerUtil;
 import org.intellij.lang.regexp.*;
 import org.intellij.lang.regexp.psi.*;
-import org.intellij.lang.regexp.psi.impl.RegExpNamedGroupRefImpl;
 import org.intellij.lang.regexp.psi.impl.RegExpGroupImpl;
 import org.jetbrains.annotations.Nls;
 import org.jetbrains.annotations.NonNls;
@@ -232,9 +232,22 @@ public final class RegExpAnnotator extends RegExpElementVisitor implements Annot
 
   @Override
   public void visitRegExpGroup(RegExpGroup group) {
+    if (RegExpGroupImpl.isPcreConditionalGroup(group.getNode())) {
+      if (RegExpGroupImpl.isPcreDefine(group.getNode())) {
+        RegExpConditional conditional = ObjectUtils.tryCast(group.getParent(), RegExpConditional.class);
+        if (conditional != null) {
+          RegExpBranch[] branches = PsiTreeUtil.getChildrenOfType(conditional, RegExpBranch.class);
+          if (branches != null && branches.length > 1) {
+            myHolder.newAnnotation(HighlightSeverity.ERROR,
+                                   RegExpBundle.message("error.define.subpattern.contains.more.than.one.branch")).create();
+          }
+        }
+      }
+      return;
+    }
     final RegExpPattern pattern = group.getPattern();
     final RegExpBranch[] branches = pattern.getBranches();
-    if (!RegExpGroupImpl.isPcreConditionalGroup(group.getNode()) && isEmpty(branches) && group.getNode().getLastChildNode().getElementType() == RegExpTT.GROUP_END) {
+    if (isEmpty(branches) && group.getNode().getLastChildNode().getElementType() == RegExpTT.GROUP_END) {
       // catches "()" as well as "(|)"
       myHolder.newAnnotation(HighlightSeverity.WARNING, RegExpBundle.message("error.empty.group")).create();
     }