diff --git a/xwords4/relay/configs.cpp b/xwords4/relay/configs.cpp
index 3152f98a4..90b222149 100644
--- a/xwords4/relay/configs.cpp
+++ b/xwords4/relay/configs.cpp
@@ -133,7 +133,9 @@ RelayConfigs::SetValueFor( const char* key, const char* value )
         m_values.erase(iter);
     }
 
-    m_values.insert( pair<const char*,const char*>(strdup(key),strdup(value) ) );
+    pair<map<const char*,const char*>::iterator,bool> result = 
+        m_values.insert( pair<const char*,const char*>(strdup(key),strdup(value) ) );
+    assert( result.second );
 }
 
 ino_t
diff --git a/xwords4/relay/crefmgr.cpp b/xwords4/relay/crefmgr.cpp
index 290475b9b..c3441f486 100644
--- a/xwords4/relay/crefmgr.cpp
+++ b/xwords4/relay/crefmgr.cpp
@@ -462,7 +462,9 @@ CRefMgr::AddNew( const char* cookie, const char* connName, CookieID cid,
 
     ref->assignConnName();
 
-    m_cookieMap.insert( pair<CookieID, CookieRef*>(ref->GetCid(), ref ) );
+    pair<CookieMap::iterator,bool> result =
+        m_cookieMap.insert( pair<CookieID, CookieRef*>(ref->GetCid(), ref ) );
+    assert( result.second );
     logf( XW_LOGINFO, "%s: paired cookie %s/connName %s with cid %d", __func__, 
           (cookie?cookie:"NULL"), connName, ref->GetCid() );
 
diff --git a/xwords4/relay/lstnrmgr.cpp b/xwords4/relay/lstnrmgr.cpp
index 098605930..d01118413 100644
--- a/xwords4/relay/lstnrmgr.cpp
+++ b/xwords4/relay/lstnrmgr.cpp
@@ -171,7 +171,9 @@ ListenerMgr::addOne( int port, bool perGame )
     success = sock != -1;
     if ( success ) {
         pair<int,bool>entry(port, perGame);
-        m_socks_to_ports.insert( pair<int,pair<int,bool> >(sock, entry ) );
+        pair<map<int,pair<int,bool> >::iterator, bool> result
+            = m_socks_to_ports.insert( pair<int,pair<int,bool> >(sock, entry ) );
+        assert( result.second );
     }
     return success;
 }