diff --git a/inst/dust/cows.cpp b/inst/dust/cows.cpp
index a591f16..6c449cd 100644
--- a/inst/dust/cows.cpp
+++ b/inst/dust/cows.cpp
@@ -210,6 +210,11 @@ class cows {
           internal.import_E[i_dst] += internal.export_E[i_src];
           internal.import_I[i_dst] += internal.export_I[i_src];
           internal.import_R[i_dst] += internal.export_R[i_src];
+        } else {
+          internal.export_S[i_src] = 0;
+          internal.export_E[i_src] = 0;
+          internal.export_I[i_src] = 0;
+          internal.export_R[i_src] = 0;
         }
       }
     }
diff --git a/src/cows.cpp b/src/cows.cpp
index fc1d9ce..8cfba97 100644
--- a/src/cows.cpp
+++ b/src/cows.cpp
@@ -212,6 +212,11 @@ class cows {
           internal.import_E[i_dst] += internal.export_E[i_src];
           internal.import_I[i_dst] += internal.export_I[i_src];
           internal.import_R[i_dst] += internal.export_R[i_src];
+        } else {
+          internal.export_S[i_src] = 0;
+          internal.export_E[i_src] = 0;
+          internal.export_I[i_src] = 0;
+          internal.export_R[i_src] = 0;
         }
       }
     }