diff --git a/src/system/kernel/messaging/KMessage.cpp b/src/system/kernel/messaging/KMessage.cpp
index c861efc599..cbeeffefd3 100644
--- a/src/system/kernel/messaging/KMessage.cpp
+++ b/src/system/kernel/messaging/KMessage.cpp
@@ -962,8 +962,16 @@ KMessage::_AllocateSpace(int32 size, bool alignAddress, bool alignSize,
 	} else {
 		if (newSize > fBufferCapacity) {
 			// if we don't own the buffer, we can't resize it
-			if (!(fFlags & KMESSAGE_OWNS_BUFFER))
+			if (!(fFlags & KMESSAGE_OWNS_BUFFER)) {
+#ifdef _KERNEL_MODE && 0
+				// optional debugging to find insufficiently sized KMessage
+				// buffers (e.g. for in-kernel notifications)
+				panic("KMessage: out of space: available: %" B_PRId32
+					", needed: %" B_PRId32 "\n", fBufferCapacity, newSize);
+#endif
 				return B_BUFFER_OVERFLOW;
+			}
+
 			int32 newCapacity = _CapacityFor(newSize);
 			void* newBuffer = realloc(fBuffer, newCapacity);
 			if (!newBuffer)