diff --git a/src/solver/parallel_tactic.cpp b/src/solver/parallel_tactic.cpp
index 61e97e040..c5b10b9b2 100644
--- a/src/solver/parallel_tactic.cpp
+++ b/src/solver/parallel_tactic.cpp
@@ -30,6 +30,7 @@ Notes:
 
 #include <thread>
 #include <mutex>
+#include <cmath>
 #include <condition_variable>
 #include "util/scoped_ptr_vector.h"
 #include "ast/ast_util.h"