diff --git a/src/math/dd/dd_bdd.cpp b/src/math/dd/dd_bdd.cpp
index 6036ae10c..940d161e1 100644
--- a/src/math/dd/dd_bdd.cpp
+++ b/src/math/dd/dd_bdd.cpp
@@ -92,6 +92,7 @@ namespace dd {
                 if (!first) throw;
                 try_reorder();
                 first = false;
+                return null_bdd;
             }
         }
         SASSERT(well_formed());
diff --git a/src/util/symbol.cpp b/src/util/symbol.cpp
index d9530c06f..42663c050 100644
--- a/src/util/symbol.cpp
+++ b/src/util/symbol.cpp
@@ -22,7 +22,7 @@ Revision History:
 #include "util/region.h"
 #include "util/string_buffer.h"
 #include <cstring>
-
+#include <thread>
 
 
 symbol symbol::m_dummy(TAG(void*, nullptr, 2));