diff --git a/CHANGES b/CHANGES
index b990bea85..7a7b52e7d 100644
--- a/CHANGES
+++ b/CHANGES
@@ -3,6 +3,9 @@
 
 Following is a brief summary of changes made in each release of Libint.
 
+- 2017-xx-yy: 2.4.1
+  - plugged leaky Engine::set_{param,oper,braket}
+
 - 2017-10-25: 2.4.0
   - changed default to use user-provided boost over bundled boost + minor fixes
 
diff --git a/include/libint2/engine.h b/include/libint2/engine.h
index 1a94a62ad..ecdf6a3da 100644
--- a/include/libint2/engine.h
+++ b/include/libint2/engine.h
@@ -468,8 +468,10 @@ class Engine {
          Params params = empty_pod(), BraKet braket = BraKet::invalid)
       : oper_(oper),
         braket_(braket),
+        primdata_(),
         spbra_(max_nprim),
         spket_(max_nprim),
+        stack_size_(0),
         lmax_(max_l),
         deriv_order_(deriv_order),
         params_(enforce_params_type(oper, params)) {
diff --git a/include/libint2/engine.impl.h b/include/libint2/engine.impl.h
index 97bacba89..3594fc4f5 100644
--- a/include/libint2/engine.impl.h
+++ b/include/libint2/engine.impl.h
@@ -589,6 +589,8 @@ __libint2_engine_inline void Engine::_initialize() {
           BOOST_PP_STRINGIZE(BOOST_PP_NBODYENGINE_MCR3_TASK(product)),         \
           hard_lmax_, lmax_);                                                  \
     }                                                                          \
+    if (stack_size_ > 0)                                                       \
+      libint2_cleanup_default(&primdata_[0]);                                  \
     stack_size_ = LIBINT2_PREFIXED_NAME(BOOST_PP_CAT(                          \
         libint2_need_memory_, BOOST_PP_NBODYENGINE_MCR3_TASK(product)))(       \
         lmax_);                                                                \