diff --git a/test_regress/t/t_vpi_get.cpp b/test_regress/t/t_vpi_get.cpp
index 592246b3b..3b1d41d07 100644
--- a/test_regress/t/t_vpi_get.cpp
+++ b/test_regress/t/t_vpi_get.cpp
@@ -202,7 +202,7 @@ int mon_check_props() {
     return 0;
 }
 
-int mon_check() {
+extern "C" int mon_check() {
     // Callback from initial block in monitor
     if (int status = mon_check_props()) return status;
     return 0;  // Ok
diff --git a/test_regress/t/t_vpi_memory.cpp b/test_regress/t/t_vpi_memory.cpp
index 3dc17b55a..b6b1a83df 100644
--- a/test_regress/t/t_vpi_memory.cpp
+++ b/test_regress/t/t_vpi_memory.cpp
@@ -213,7 +213,7 @@ void _mon_check_memory() {
     }
 }
 
-int mon_check() {
+extern "C" int mon_check() {
     // Callback from initial block in monitor
     _mon_check_memory();
     return errors;
diff --git a/test_regress/t/t_vpi_param.cpp b/test_regress/t/t_vpi_param.cpp
index ac6275b15..cee164fe3 100644
--- a/test_regress/t/t_vpi_param.cpp
+++ b/test_regress/t/t_vpi_param.cpp
@@ -203,7 +203,7 @@ int _mon_check_param() {
     return status;
 }
 
-int mon_check() {
+extern "C" int mon_check() {
     // Callback from initial block in monitor
     if (int status = _mon_check_param()) return status;
     return 0;  // Ok
diff --git a/test_regress/t/t_vpi_unimpl.cpp b/test_regress/t/t_vpi_unimpl.cpp
index 5706be271..816c9eca3 100644
--- a/test_regress/t/t_vpi_unimpl.cpp
+++ b/test_regress/t/t_vpi_unimpl.cpp
@@ -176,7 +176,7 @@ int _mon_check_unimpl(p_cb_data cb_data) {
     return 0;  // Ok
 }
 
-int mon_check() {
+extern "C" int mon_check() {
     // Callback from initial block in monitor
     if (int status = _mon_check_unimpl(NULL)) return status;
     return 0;  // Ok
diff --git a/test_regress/t/t_vpi_var.cpp b/test_regress/t/t_vpi_var.cpp
index 9ddd720e2..2861d58b8 100644
--- a/test_regress/t/t_vpi_var.cpp
+++ b/test_regress/t/t_vpi_var.cpp
@@ -638,7 +638,7 @@ int _mon_check_vlog_info() {
     return 0;
 }
 
-int mon_check() {
+extern "C" int mon_check() {
     // Callback from initial block in monitor
 #ifdef TEST_VERBOSE
     printf("-mon_check()\n");