1 files changed, 6 insertions, 1 deletions
diff --git a/src/main/java/org/zwobble/couscous/MapBackedProject.java b/src/main/java/org/zwobble/couscous/MapBackedProject.java
index 7a243f4..8547677 100644
--- a/src/main/java/org/zwobble/couscous/MapBackedProject.java
+++ b/src/main/java/org/zwobble/couscous/MapBackedProject.java
@@ -46,6 +46,11 @@ public class MapBackedProject implements Project {
     
     @Override
     public ConcreteType findClass(TypeName name) {
-        return classes.get(name);
+        if (classes.containsKey(name)) {
+            return classes.get(name);            
+        } else {
+            throw new IllegalArgumentException("Cannot find class: " + name);
+        }
+        
     }
 }