diff --git a/src/crl.c b/src/crl.c
index 27a133567..e4f49a755 100644
--- a/src/crl.c
+++ b/src/crl.c
@@ -1640,7 +1640,7 @@ static int StopMonitor(wolfSSL_CRL_mfd_t mfd)
 
 #ifdef DEBUG_WOLFSSL
 #define SHOW_WINDOWS_ERROR() do {                               \
-    LPVOID lpMsgBuf;                                            \
+    LPVOID lpMsgBuf = NULL;                                     \
     DWORD dw = GetLastError();                                  \
     FormatMessageA(                                             \
         FORMAT_MESSAGE_ALLOCATE_BUFFER |                        \