diff --git a/src/pkcs11/pkcs11-global.c b/src/pkcs11/pkcs11-global.c
index a3260314..67189030 100644
--- a/src/pkcs11/pkcs11-global.c
+++ b/src/pkcs11/pkcs11-global.c
@@ -456,7 +456,12 @@ CK_RV C_GetSlotList(CK_BBOOL       tokenPresent,  /* only slots with token prese
 
 	card_detect_all();
 
-	DEBUG_VSS(NULL, "C_GetSlotList after card_detect_all");
+	if (list_empty(&virtual_slots)) {
+		sc_log(context, "returned 0 slots\n");
+		*pulCount = 0;
+		rv = CKR_OK;
+		goto out;
+	}
 
 	found = calloc(list_size(&virtual_slots), sizeof(CK_SLOT_ID));
 
diff --git a/win32/Make.rules.mak b/win32/Make.rules.mak
index 4f4971a7..c6b1aac3 100644
--- a/win32/Make.rules.mak
+++ b/win32/Make.rules.mak
@@ -1,7 +1,7 @@
 OPENSC_FEATURES = pcsc
 
 #Include support for minidriver
-MINIDRIVER_DEF = /DENABLE_MINIDRIVER
+#MINIDRIVER_DEF = /DENABLE_MINIDRIVER
 
 #Build MSI with the Windows Installer XML (WIX) toolkit, requires WIX >= 3.9
 !IF "$(WIX)" == ""
@@ -33,7 +33,7 @@ WIX_LIBS = "$(WIX)\SDK\$(WIXVSVER)\lib\$(PLATFORM)\dutil.lib" "$(WIX)\SDK\$(WIXV
 SM_DEF = /DENABLE_SM
 
 #Build with debugging support
-#DEBUG_DEF = /DDEBUG
+DEBUG_DEF = /DDEBUG
 
 # If you want support for OpenSSL (needed for pkcs15-init tool, software hashing in PKCS#11 library and verification):
 # - download and build OpenSSL
diff --git a/win32/winconfig.h.in b/win32/winconfig.h.in
index 94ed9b54..fa682c5b 100644
--- a/win32/winconfig.h.in
+++ b/win32/winconfig.h.in
@@ -103,6 +103,8 @@
 #define DEFAULT_ONEPIN_PKCS11_PROVIDER "@DEFAULT_ONEPIN_PKCS11_PROVIDER@"
 #endif
 
+#define PKCS11_THREAD_LOCKING
+
 #ifndef DEFAULT_SM_MODULE
 #define DEFAULT_SM_MODULE "@DEFAULT_SM_MODULE@"
 #endif