diff --git a/src/procedure2/PrimitiveRegistry.cpp b/src/procedure2/PrimitiveRegistry.cpp
index 0ce7aa6..e62b679 100644
--- a/src/procedure2/PrimitiveRegistry.cpp
+++ b/src/procedure2/PrimitiveRegistry.cpp
@@ -41,6 +41,7 @@ namespace xo {
                 log && log("do install fn (", i+1, "/", n, ")");
 
                 ok = ok & fn(mm, sink, flags);
+                ++i;
             }
 
             return ok;