diff --git a/src/osdep/osdep.c b/src/osdep/osdep.c
index 66778f01..c056916d 100644
--- a/src/osdep/osdep.c
+++ b/src/osdep/osdep.c
@@ -74,7 +74,7 @@
 #include "util/string.h"
 
 
-#if !defined(CONFIG_OS_DOS) && !defined(CONFIG_OS_UNIX)
+#if !defined(CONFIG_OS_DOS) && !defined(CONFIG_OS_UNIX) && !defined(CONFIG_OS_WIN32)
 long
 os_get_free_mem_in_mib(void)
 {
diff --git a/src/osdep/win32/win32.c b/src/osdep/win32/win32.c
index aa27d1d7..7347e209 100644
--- a/src/osdep/win32/win32.c
+++ b/src/osdep/win32/win32.c
@@ -336,3 +336,13 @@ user_appdata_directory(void)
 	else
 		return NULL;
 }
+
+long
+os_get_free_mem_in_mib(void)
+{
+	MEMORYSTATUSEX statex;
+	statex.dwLength = sizeof(statex);
+	GlobalMemoryStatusEx(&statex);
+
+	return statex.ullAvailPhys / (1024 * 1024);
+}