--- a/test-tool/iscsi-support.c
+++ b/test-tool/iscsi-support.c
@@ -119,7 +119,8 @@ int readonly;
 int sbc3_support;
 int maximum_transfer_length;
 
-int (*real_iscsi_queue_pdu)(struct iscsi_context *iscsi, struct iscsi_pdu *pdu);
+static int (*real_iscsi_queue_pdu)(struct iscsi_context *iscsi, struct iscsi_pdu *pdu);
+int (*local_iscsi_queue_pdu)(struct iscsi_context *iscsi, struct iscsi_pdu *pdu);
 
 static const unsigned char zeroBlock[4096];
 
--- a/test-tool/iscsi-support.h
+++ b/test-tool/iscsi-support.h
@@ -779,7 +779,7 @@ struct iscsi_async_state {
 void wait_until_test_finished(struct iscsi_context *iscsi, struct iscsi_async_state *test_state);
 
 struct iscsi_pdu;
-int (*local_iscsi_queue_pdu)(struct iscsi_context *iscsi, struct iscsi_pdu *pdu);
+extern int (*local_iscsi_queue_pdu)(struct iscsi_context *iscsi, struct iscsi_pdu *pdu);
 
 struct scsi_command_descriptor *get_command_descriptor(int opcode, int sa);
 
--- a/test-tool/iscsi-test-cu.c
+++ b/test-tool/iscsi-test-cu.c
@@ -63,7 +63,7 @@ static unsigned int maxsectors;
  * this allows us to redefine how PDU are queued, at times, for
  * testing purposes
  */
-int (*real_iscsi_queue_pdu)(struct iscsi_context *iscsi, struct iscsi_pdu *pdu);
+int (*real_iscsi_queue_pdu)(struct iscsi_context *iscsi, struct iscsi_pdu *pdu) = NULL;
 
 /*****************************************************************
  *