1 files changed, 9 insertions, 0 deletions

diff --git a/src/cuchaz/enigma/mapping/Mappings.java b/src/cuchaz/enigma/mapping/Mappings.java
index c7cb6a6..f3b8fad 100644
--- a/src/cuchaz/enigma/mapping/Mappings.java
+++ b/src/cuchaz/enigma/mapping/Mappings.java
@@ -70,8 +70,17 @@ public class Mappings implements Serializable
         
         protected void addClassMapping( ClassMapping classMapping )
         {
+                if( m_classesByObf.containsKey( classMapping.getObfName() ) )
+                {
+                        throw new Error( "Already have mapping for " + classMapping.getObfName() );
+                }
+                if( m_classesByDeobf.containsKey( classMapping.getDeobfName() ) )
+                {
+                        throw new Error( "Already have mapping for " + classMapping.getDeobfName() );
+                }
                 m_classesByObf.put( classMapping.getObfName(), classMapping );
                 m_classesByDeobf.put( classMapping.getDeobfName(), classMapping );
+                assert( m_classesByObf.size() == m_classesByDeobf.size() );
         }
         
         public ClassMapping getClassByObf( ClassEntry entry )