diff --git a/vpnor/test/write_patch.cpp b/vpnor/test/write_patch.cpp
index 1a3e4ee..a146bcf 100644
--- a/vpnor/test/write_patch.cpp
+++ b/vpnor/test/write_patch.cpp
@@ -12,7 +12,9 @@
 #include "config.h"
 #include "common.h"
 #include "mbox.h"
+extern "C" {
 #include "flash.h"
+}
 
 #include "vpnor/test/tmpd.hpp"
 
diff --git a/vpnor/test/write_patch_resize.cpp b/vpnor/test/write_patch_resize.cpp
index 5d39802..ff2558b 100644
--- a/vpnor/test/write_patch_resize.cpp
+++ b/vpnor/test/write_patch_resize.cpp
@@ -13,7 +13,10 @@
 #include "config.h"
 #include "common.h"
 #include "mbox.h"
+
+extern "C" {
 #include "flash.h"
+}
 
 #include "vpnor/test/tmpd.hpp"
 
diff --git a/vpnor/test/write_prsv.cpp b/vpnor/test/write_prsv.cpp
index f880476..b89b954 100644
--- a/vpnor/test/write_prsv.cpp
+++ b/vpnor/test/write_prsv.cpp
@@ -10,7 +10,9 @@
 
 #include "common.h"
 #include "mbox.h"
+extern "C" {
 #include "flash.h"
+}
 
 #include "vpnor/test/tmpd.hpp"
 
diff --git a/vpnor/test/write_ro.cpp b/vpnor/test/write_ro.cpp
index f0dd215..24a534a 100644
--- a/vpnor/test/write_ro.cpp
+++ b/vpnor/test/write_ro.cpp
@@ -10,7 +10,10 @@
 
 #include "common.h"
 #include "mbox.h"
+
+extern "C" {
 #include "flash.h"
+}
 
 #include "vpnor/test/tmpd.hpp"
 
diff --git a/vpnor/test/write_rw.cpp b/vpnor/test/write_rw.cpp
index 7760fc7..76b1525 100644
--- a/vpnor/test/write_rw.cpp
+++ b/vpnor/test/write_rw.cpp
@@ -10,7 +10,9 @@
 
 #include "common.h"
 #include "mbox.h"
+extern "C" {
 #include "flash.h"
+}
 
 #include "vpnor/test/tmpd.hpp"