diff --git a/src/java/net/kaleidos/hibernate/criterion/hstore/PgHstoreOperatorExpression.java b/src/java/net/kaleidos/hibernate/criterion/hstore/PgHstoreOperatorExpression.java
index 9709631..f22982b 100644
--- a/src/java/net/kaleidos/hibernate/criterion/hstore/PgHstoreOperatorExpression.java
+++ b/src/java/net/kaleidos/hibernate/criterion/hstore/PgHstoreOperatorExpression.java
@@ -21,12 +21,12 @@ public class PgHstoreOperatorExpression implements Criterion {
     private static final long serialVersionUID = 2872183637309166619L;
 
     private final String propertyName;
-    private final Map<String,String> value;
+    private final Map<Object,String> value;
     private final String operator;
 
     private static final TypedValue[] NO_VALUES = new TypedValue[0];
 
-    protected PgHstoreOperatorExpression(String propertyName, Map<String,String> value, String operator) {
+    protected PgHstoreOperatorExpression(String propertyName, Map<Object,String> value, String operator) {
         this.propertyName = propertyName;
         this.value = value;
         this.operator = operator;
diff --git a/src/java/net/kaleidos/hibernate/usertype/HstoreHelper.java b/src/java/net/kaleidos/hibernate/usertype/HstoreHelper.java
index 7f4e299..2b95cdc 100644
--- a/src/java/net/kaleidos/hibernate/usertype/HstoreHelper.java
+++ b/src/java/net/kaleidos/hibernate/usertype/HstoreHelper.java
@@ -19,7 +19,7 @@ private static String escapeQuotes(String text) {
         return text.replaceAll("\"", "'");
     }
 
-    public static String toString(Map<String, String> m) {
+    public static String toString(Map<Object, String> m) {
         if (m == null || m.isEmpty()) {
             return "";
         }
@@ -77,4 +77,4 @@ public static HstoreDomainType toMap(String s) {
 
         return new HstoreDomainType(m);
     }
-}
\ No newline at end of file
+}
diff --git a/src/java/net/kaleidos/hibernate/usertype/HstoreType.java b/src/java/net/kaleidos/hibernate/usertype/HstoreType.java
index 761bfdb..e39c96c 100644
--- a/src/java/net/kaleidos/hibernate/usertype/HstoreType.java
+++ b/src/java/net/kaleidos/hibernate/usertype/HstoreType.java
@@ -6,6 +6,7 @@
 import java.sql.SQLException;
 import java.sql.Types;
 import java.util.HashMap;
+import java.util.TreeMap;
 import java.util.Map;
 
 import net.kaleidos.hibernate.postgresql.hstore.HstoreDomainType;
@@ -39,8 +40,20 @@ public Class<?> returnedClass() {
     @Override
     @SuppressWarnings("rawtypes")
     public boolean equals(Object x, Object y) throws HibernateException {
-        Map m1 = (Map) x;
-        Map m2 = ((HstoreDomainType)y).getDataStore();
+        Map m1;
+        Map m2;
+        if (x instanceof HstoreDomainType){
+            m1 = ((HstoreDomainType)x).getDataStore();
+        } else {
+            m1 = (Map) x;
+        }
+
+        if (y instanceof HstoreDomainType){
+            m2 = ((HstoreDomainType)y).getDataStore();
+        } else {
+            m2 = (Map) y;
+        }
+        
         return m1.equals(m2);
     }
 
@@ -53,7 +66,12 @@ public int hashCode(Object x) throws HibernateException {
     @SuppressWarnings({ "rawtypes", "unchecked" })
     public Object deepCopy(Object value) throws HibernateException {
         if (value != null) {
-            Map m = ((HstoreDomainType)value).getDataStore();
+            Map m;
+            if (value instanceof HstoreDomainType)
+                m = ((HstoreDomainType)value).getDataStore();
+            else
+                m = (Map)value;
+
             if (m == null) {
                 m = new HashMap();
             }
diff --git a/test/integration/net/kaleidos/hibernate/hstore/PostgresqlHstoreDomainIntegrationSpec.groovy b/test/integration/net/kaleidos/hibernate/hstore/PostgresqlHstoreDomainIntegrationSpec.groovy
index 83cfa32..5d63a41 100644
--- a/test/integration/net/kaleidos/hibernate/hstore/PostgresqlHstoreDomainIntegrationSpec.groovy
+++ b/test/integration/net/kaleidos/hibernate/hstore/PostgresqlHstoreDomainIntegrationSpec.groovy
@@ -68,4 +68,22 @@ class PostgresqlHstoreDomainIntegrationSpec extends IntegrationSpec {
             ["foo,bar":"baz,qux"]  | 'foo,bar'         | 0
             [foo:"bar"]            | 'xxx'             | 1
     }
-}
\ No newline at end of file
+    
+    @Unroll
+    void 'save and delete a domain class with a map. key: #data'() {
+        setup:
+            def testHstore = new TestHstore(testAttributes: data)
+        when: 'I save an instance'
+            testHstore.save(flush: true)
+        and: 'I try to delete it'
+            testHstore.delete(flush: true)
+        
+        then: 'It shouldn\'t be present in database anymore'
+            TestHstore.count() == 0
+
+        where:
+            data                  | attribute | value
+            [foo:"bar"]           | "foo"     | "bar"
+            ["foo,bar":"baz,qux"] | "foo,bar" | "baz,qux"
+    }
+}