diff --git a/src/test/dl_product_relation.cpp b/src/test/dl_product_relation.cpp
index 352748087..e418d5ea0 100644
--- a/src/test/dl_product_relation.cpp
+++ b/src/test/dl_product_relation.cpp
@@ -11,6 +11,7 @@ Copyright (c) 2015 Microsoft Corporation
 #include "muz/rel/dl_finite_product_relation.h"
 #include "muz/rel/dl_sparse_table.h"
 #include "muz/rel/rel_context.h"
+#include <iostream>
 
 namespace datalog {
 
diff --git a/src/test/dl_relation.cpp b/src/test/dl_relation.cpp
index 1940de3e9..a69e44cd2 100644
--- a/src/test/dl_relation.cpp
+++ b/src/test/dl_relation.cpp
@@ -14,6 +14,7 @@ Copyright (c) 2015 Microsoft Corporation
 #include "muz/rel/dl_bound_relation.h"
 #include "muz/rel/dl_product_relation.h"
 #include "util/util.h"
+#include <iostream>
 
 namespace datalog {
 
diff --git a/src/test/matcher.cpp b/src/test/matcher.cpp
index 68f37ccb6..6d5576714 100644
--- a/src/test/matcher.cpp
+++ b/src/test/matcher.cpp
@@ -20,7 +20,7 @@ Revision History:
 #include "ast/substitution/matcher.h"
 #include "ast/ast_pp.h"
 #include "ast/reg_decl_plugins.h"
-
+#include <iostream>
 
 void tst_match(ast_manager & m, app * t, app * i) {
     substitution s(m);
diff --git a/src/test/quant_elim.cpp b/src/test/quant_elim.cpp
index f376e2c1d..8fd5416a1 100644
--- a/src/test/quant_elim.cpp
+++ b/src/test/quant_elim.cpp
@@ -11,7 +11,7 @@ Copyright (c) 2015 Microsoft Corporation
 #include "util/lbool.h"
 #include <sstream>
 #include "ast/reg_decl_plugins.h"
-
+#include <iostream>
 
 #if 0
 static void test_qe(ast_manager& m, lbool expected_outcome, expr* fml, char const* option) {