diff --git a/lib/aos/paging.c b/lib/aos/paging.c
index 2a63f53..7b14290 100644
--- a/lib/aos/paging.c
+++ b/lib/aos/paging.c
@@ -126,29 +126,35 @@ static void pt_exception_handler(enum exception_type type, int subtype,
     }
     if (vaddr_reg == NULL) {
         debug_printf("[pt_exception_handler] page_addr = 0x%x\n", page_addr);
+        thread_mutex_unlock(&st->lock);
         USER_PANIC("[pt_exception_handler][ERROR] Page fault ouside valid virtual address space");
     }
     if (vaddr_reg->free) {
         debug_printf("[pt_exception_handler] page_addr = 0x%x, base = 0x%x, size = 0x%x\n", page_addr, vaddr_reg->base, vaddr_reg->size);
+        thread_mutex_unlock(&st->lock);
         USER_PANIC("[pt_exception_handler][ERROR] Page fault ouside allocated address space");
     }
     if (!vaddr_reg->heap) {
+        thread_mutex_unlock(&st->lock);
         USER_PANIC("[ERROR] Page fault in allocated address space but outside heap");
     }
 
     if (is_mapped(st, page_addr)) {
         // Page has already been mapped by another thread before we took the lock.
+        thread_mutex_unlock(&st->lock);
         return;
     }
 
     struct capref frame;
     err = frame_alloc(&frame, BASE_PAGE_SIZE, NULL);
     if (err_is_fail(err)) {
+        thread_mutex_unlock(&st->lock);
         USER_PANIC_ERR(err, "Failed to allocate frame in page fault handler");
     }
 
     err = _paging_map_fixed_attr(st, page_addr, frame, BASE_PAGE_SIZE, VREGION_FLAGS_READ_WRITE);
     if (err_is_fail(err)) {
+        thread_mutex_unlock(&st->lock);
         USER_PANIC_ERR(err, "Failed to map frame in page fault handler");
     }