diff --git a/src/viewer/svutil.cpp b/src/viewer/svutil.cpp
index 3868bc76e47ad1983cf53082ae99dc5232feaf03..99de09581fe6fab82ee4d8926bc7d7899b9d4e44 100644
--- a/src/viewer/svutil.cpp
+++ b/src/viewer/svutil.cpp
@@ -279,6 +279,8 @@ void SVNetwork::Close() {
 #else
   close(stream_);
 #endif
+  // Mark stream_ as invalid.
+  stream_ = -1;
 }
 
 
@@ -448,6 +450,7 @@ SVNetwork::SVNetwork(const char* hostname, int port) {
 }
 
 SVNetwork::~SVNetwork() {
+  Close();
   delete[] msg_buffer_in_;
 }