diff --git a/m3.py b/m3.py
index 93df7b7..d4fce41 100644
--- a/m3.py
+++ b/m3.py
@@ -197,6 +197,7 @@ def validateInstance(self, instance, instanceName):
             except AttributeError:
                 raise Exception("%s does not have a field called %s%n" % (instanceName, field.name))
                 raise
+            field.validateContent(fieldContent, instanceName + "." + field.name);
 
     def hasField(self, fieldName):
         return fieldName in self.nameToFieldMap