diff -r d13adbcebf0c src/compiler/UocInfo.cxx
--- a/src/compiler/UocInfo.cxx	Tue Oct 19 14:34:41 2010 -0700
+++ b/src/compiler/UocInfo.cxx	Tue Oct 26 12:13:03 2010 -0700
@@ -266,8 +266,18 @@
   }
 
   // If we survived the compile, the interface is now in the ifList
-  // and can be found.
-  return findInterface(ifName);
+  // and can be found if the imported file declared it.
+  puoci = findInterface(ifName);
+
+  if (!puoci) {
+    errStream
+      << loc.asString() << ": "
+      << "Import did not declare interface \"" << ifName << "\".\n";
+
+    exit(1);
+  }
+
+  return puoci;
 }
 
 bool