diff --git a/src/api/api_solver.cpp b/src/api/api_solver.cpp
index a7bb5a627..0bf74b840 100644
--- a/src/api/api_solver.cpp
+++ b/src/api/api_solver.cpp
@@ -100,9 +100,7 @@ extern "C" {
 
     solver2smt2_pp::solver2smt2_pp(ast_manager& m, char const* file): m_pp_util(m), m_out(file) {
         if (!m_out) {
-            std::string msg;
-            msg = msg + "could not open " + file + " for output";
-            throw default_exception(msg.c_str());
+            throw default_exception("could not open " + std::string(file) + " for output");
         }
     }
 
diff --git a/src/api/z3_replayer.cpp b/src/api/z3_replayer.cpp
index e898f2720..09cc8bba4 100644
--- a/src/api/z3_replayer.cpp
+++ b/src/api/z3_replayer.cpp
@@ -79,7 +79,7 @@ struct z3_replayer::imp {
             strm << "expecting " << kind2string(k) << " at position "
                  << pos << " but got " << kind2string(m_args[pos].m_kind);
             TRACE("z3_replayer", tout << strm.str() << "\n";);
-            throw z3_replayer_exception(strm.str().c_str());
+            throw z3_replayer_exception(strm.str());
         }
     }
 
diff --git a/src/sat/sat_solver.cpp b/src/sat/sat_solver.cpp
index 9a1f9c01d..ea283895c 100644
--- a/src/sat/sat_solver.cpp
+++ b/src/sat/sat_solver.cpp
@@ -1464,7 +1464,7 @@ namespace sat {
         if (finished_id == -1) {
             switch (ex_kind) {
             case ERROR_EX: throw z3_error(error_code);
-            default: throw default_exception(ex_msg.c_str());
+            default: throw default_exception(std::move(ex_msg));
             }
         }
         return result;