diff --git a/querydsl-core/src/main/java/com/mysema/query/BooleanBuilder.java b/querydsl-core/src/main/java/com/mysema/query/BooleanBuilder.java
index 377da3407..b3869a389 100644
--- a/querydsl-core/src/main/java/com/mysema/query/BooleanBuilder.java
+++ b/querydsl-core/src/main/java/com/mysema/query/BooleanBuilder.java
@@ -10,6 +10,8 @@ import java.util.List;
 
 import javax.annotation.Nullable;
 
+import org.apache.commons.lang.ObjectUtils;
+
 import com.mysema.query.types.Expr;
 import com.mysema.query.types.Operation;
 import com.mysema.query.types.Operator;
@@ -84,7 +86,7 @@ public final class BooleanBuilder extends EBoolean implements Cloneable, Operati
         if (o == this){
             return true;
         }else if (o instanceof BooleanBuilder){
-            return ((BooleanBuilder)o).getValue().equals(expr);    
+            return ObjectUtils.equals(((BooleanBuilder)o).getValue(), expr);
         }else{
             return false;
         }               
diff --git a/querydsl-core/src/main/java/com/mysema/query/DefaultQueryMetadata.java b/querydsl-core/src/main/java/com/mysema/query/DefaultQueryMetadata.java
index 1d9cfe770..8ee0d3740 100644
--- a/querydsl-core/src/main/java/com/mysema/query/DefaultQueryMetadata.java
+++ b/querydsl-core/src/main/java/com/mysema/query/DefaultQueryMetadata.java
@@ -88,7 +88,7 @@ public class DefaultQueryMetadata implements QueryMetadata, Cloneable {
     @Override
     public void addJoinCondition(EBoolean o) {
         if (!joins.isEmpty()) {
-            joins.get(joins.size() - 1).setCondition(o);
+            joins.get(joins.size() - 1).addCondition(o);
         }
     }
 
diff --git a/querydsl-core/src/main/java/com/mysema/query/JoinExpression.java b/querydsl-core/src/main/java/com/mysema/query/JoinExpression.java
index c3888e0b6..d6c95ac52 100644
--- a/querydsl-core/src/main/java/com/mysema/query/JoinExpression.java
+++ b/querydsl-core/src/main/java/com/mysema/query/JoinExpression.java
@@ -21,8 +21,7 @@ import com.mysema.query.types.expr.EBoolean;
  */
 public final class JoinExpression {
     
-    // mutable
-    private EBoolean condition;
+    private BooleanBuilder condition = new BooleanBuilder();
 
     private final Set<Object> flags = new HashSet<Object>();
 
@@ -36,11 +35,11 @@ public final class JoinExpression {
     }
 
     public EBoolean getCondition() {
-        return condition;
+        return condition.getValue();
     }
 
-    public void setCondition(EBoolean condition) {
-        this.condition = condition;
+    public void addCondition(EBoolean c) {
+        condition.and(c);
     }
 
     public Expr<?> getTarget() {
@@ -66,7 +65,7 @@ public final class JoinExpression {
     public String toString() {
         StringBuilder builder = new StringBuilder();
         builder.append(type).append(" ").append(target);
-        if (condition != null) {
+        if (condition.getValue() != null) {
             builder.append(" ON ").append(condition);
         }
         return builder.toString();
diff --git a/querydsl-core/src/test/java/com/mysema/query/JoinExpressionTest.java b/querydsl-core/src/test/java/com/mysema/query/JoinExpressionTest.java
index 0834960de..4b4bb08b0 100644
--- a/querydsl-core/src/test/java/com/mysema/query/JoinExpressionTest.java
+++ b/querydsl-core/src/test/java/com/mysema/query/JoinExpressionTest.java
@@ -24,9 +24,12 @@ public class JoinExpressionTest {
     }
 
     @Test
-    public void testSetCondition() {
-	je.setCondition(EBooleanConst.TRUE);
+    public void testAddCondition() {
+	je.addCondition(EBooleanConst.TRUE);
 	assertEquals(EBooleanConst.TRUE, je.getCondition());
+	
+	je.addCondition(EBooleanConst.FALSE);
+	assertEquals(EBooleanConst.TRUE.and(EBooleanConst.FALSE), je.getCondition());
     }
 
     @Test
diff --git a/querydsl-core/src/test/java/com/mysema/query/support/QueryMixinTest.java b/querydsl-core/src/test/java/com/mysema/query/support/QueryMixinTest.java
new file mode 100644
index 000000000..50a0dbbd9
--- /dev/null
+++ b/querydsl-core/src/test/java/com/mysema/query/support/QueryMixinTest.java
@@ -0,0 +1,41 @@
+package com.mysema.query.support;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+import org.junit.Test;
+
+import com.mysema.query.JoinExpression;
+import com.mysema.query.domain.QCommonPersistence;
+import com.mysema.query.types.expr.EBoolean;
+import com.mysema.query.types.path.PathMetadataFactory;
+
+
+public class QueryMixinTest {
+    
+    private QueryMixin<?> mixin = new QueryMixin();
+    
+    private QCommonPersistence entity = new QCommonPersistence(PathMetadataFactory.forVariable("entity"));
+    
+    @Test
+    public void getJoins_with_condition(){               
+        mixin.innerJoin(entity);
+        mixin.on(entity.version.isNull(), entity.version.isNotNull());
+        
+        assertEquals(1, mixin.getMetadata().getJoins().size());
+        JoinExpression je = mixin.getMetadata().getJoins().get(0);
+        assertEquals(entity, je.getTarget());
+        assertEquals(EBoolean.allOf(entity.version.isNull(), entity.version.isNotNull()), je.getCondition());
+    }
+    
+    @Test
+    public void getJoins_no_condition(){
+        mixin.innerJoin(entity);
+        
+        assertEquals(1, mixin.getMetadata().getJoins().size());
+        JoinExpression je = mixin.getMetadata().getJoins().get(0);
+        assertEquals(entity, je.getTarget());
+        assertNull(je.getCondition());
+    }
+
+}