diff --git a/src/sem/ntapi_sem_ioctl.c b/src/sem/ntapi_sem_ioctl.c
index 9735dfc..5c6a0a1 100644
--- a/src/sem/ntapi_sem_ioctl.c
+++ b/src/sem/ntapi_sem_ioctl.c
@@ -15,10 +15,18 @@
 #include "ntapi_impl.h"
 
 static int32_t __sem_ioctl_return(
+	void *		mapaddr,
 	intptr_t *	hlock,
 	int32_t		status)
 {
-	at_store(hlock,0);
+	if (hlock)
+		at_store(hlock,0);
+
+	if (mapaddr)
+		__ntapi->zw_unmap_view_of_section(
+			NT_CURRENT_PROCESS_HANDLE,
+			mapaddr);
+
 	return status;
 }
 
@@ -36,6 +44,7 @@ int32_t	__stdcall __ntapi_sem_ioctl(
 	__in	uint32_t		output_buffer_length)
 {
 	int32_t			status;
+	void *			mapaddr;
 	void *			hsection;
 	void *			secaddr;
 	size_t			secsize;
@@ -63,20 +72,28 @@ int32_t	__stdcall __ntapi_sem_ioctl(
 		hsection = sem->section;
 		secaddr  = sem->section_addr;
 		secsize  = sem->section_size;
+		mapaddr  = 0;
 
 	} else if ((status = __ntapi->ipc_init_section_by_port(
 			sem->hport,&hsection,
 			&secaddr,&secsize)))
 		return status;
 
+	else
+		mapaddr = secaddr;
+
 	if (input_buffer_length > secsize)
-		return NT_STATUS_INFO_LENGTH_MISMATCH;
+		return __sem_ioctl_return(
+			mapaddr,0,
+			NT_STATUS_INFO_LENGTH_MISMATCH);
 
 	/* lock */
 	hlock = &(__ntapi_internals()->hlock);
 
 	if (at_locked_cas(hlock,0,1))
-		return NT_STATUS_RESOURCE_NOT_OWNED;
+		return __sem_ioctl_return(
+			mapaddr,0,
+			NT_STATUS_RESOURCE_NOT_OWNED);
 
 	/* semop array to section */
 	__ntapi->tt_generic_memcpy(
@@ -104,12 +121,12 @@ int32_t	__stdcall __ntapi_sem_ioctl(
 	msg.data.seminfo.riosb		= iosb;
 
 	if ((status = __ntapi->zw_request_wait_reply_port(sem->hport,&msg,&msg)))
-		return __sem_ioctl_return(hlock,status);
+		return __sem_ioctl_return(mapaddr,hlock,status);
 	else if (msg.data.ttyinfo.status)
-		return __sem_ioctl_return(hlock,msg.data.ttyinfo.status);
+		return __sem_ioctl_return(mapaddr,hlock,msg.data.ttyinfo.status);
 
 	iosb->status = NT_STATUS_SUCCESS;
 	iosb->info   = 0;
 
-	return __sem_ioctl_return(hlock,NT_STATUS_SUCCESS);
+	return __sem_ioctl_return(mapaddr,hlock,NT_STATUS_SUCCESS);
 }