--- w/sys/kern/kern_malloc.c	
+++ w/sys/kern/kern_malloc.c	
@@ -472,9 +472,12 @@ malloc(unsigned long size, struct malloc_type *mtp, int flags)
 		}
 	}
 #endif
-	if (flags & M_WAITOK)
+	if (flags & M_WAITOK) {
 		KASSERT(curthread->td_intr_nesting_level == 0,
 		   ("malloc(M_WAITOK) in interrupt context"));
+		KASSERT(THREAD_CAN_SLEEP(),
+		   ("malloc(M_WAITOK) in no_sleeping context"));
+	}
 
 #ifdef DEBUG_MEMGUARD
 	if (memguard_cmp_mtp(mtp, size)) {