diff --git a/dlls/mapi32/mapi32_main.c b/dlls/mapi32/mapi32_main.c
index 6c35563a448..e7c17812327 100644
--- a/dlls/mapi32/mapi32_main.c
+++ b/dlls/mapi32/mapi32_main.c
@@ -33,8 +33,8 @@
 
 WINE_DEFAULT_DEBUG_CHANNEL(mapi);
 
-LONG MAPI_ObjectCount = 0;
-HINSTANCE hInstMAPI32;
+DECLSPEC_HIDDEN LONG MAPI_ObjectCount = 0;
+DECLSPEC_HIDDEN HINSTANCE hInstMAPI32;
 
 /***********************************************************************
  *              DllMain (MAPI32.init)
diff --git a/dlls/mapi32/util.h b/dlls/mapi32/util.h
index df03d6e5f9a..6fbf81e3aee 100644
--- a/dlls/mapi32/util.h
+++ b/dlls/mapi32/util.h
@@ -25,8 +25,8 @@
 #include <mapi.h>
 #include <mapix.h>
 
-extern void load_mapi_providers(void);
-extern void unload_mapi_providers(void);
+extern void load_mapi_providers(void) DECLSPEC_HIDDEN;
+extern void unload_mapi_providers(void) DECLSPEC_HIDDEN;
 
 typedef struct MAPI_FUNCTIONS {
     LPMAPIADDRESS        MAPIAddress;
@@ -60,7 +60,7 @@ typedef struct MAPI_FUNCTIONS {
     SCODE    (WINAPI *ScInitMapiUtil)             (ULONG ulReserved);
 } MAPI_FUNCTIONS;
 
-extern MAPI_FUNCTIONS mapiFunctions;
-extern HINSTANCE hInstMAPI32;
+extern MAPI_FUNCTIONS mapiFunctions DECLSPEC_HIDDEN;
+extern HINSTANCE hInstMAPI32 DECLSPEC_HIDDEN;
 
 #endif