1 files changed, 4 insertions, 0 deletions
diff --git a/st/SymbolTable.java b/st/SymbolTable.java
index 0fca239..fa196e3 100644
--- a/st/SymbolTable.java
+++ b/st/SymbolTable.java
@@ -52,6 +52,10 @@ public class SymbolTable {
         ClassInstance cls = (ClassInstance) this.active.get(TypeEnum.classname);
         ClassInstance ext = this.getClass(arg);
 
+        if (ext == null)
+            throw new TypecheckException(String.format("There is no %s to extend!",
+                                                       arg));
+
         MinimalLogger.info(String.format("%s found to extend %s",
                                          cls.getName(),
                                          ext.getName()));