diff --git a/src/DocIterator.cpp b/src/DocIterator.cpp
index 80e67ee2cf..6548186fd7 100644
--- a/src/DocIterator.cpp
+++ b/src/DocIterator.cpp
@@ -535,7 +535,9 @@ bool DocIterator::fixIfBroken()
 	size_t n = slices_.size();
 	for (; i != n; ++i) {
 		CursorSlice & cs = slices_[i];
-		if (&cs.inset() != inset || cs.nargs() == 0) {
+		if (&cs.inset() != inset
+		    || (cs.inset().inMathed() ? ! cs.inset().isActive()
+		                              : ! cs.inset().editable())) {
 			// the whole slice is wrong, chop off this as well
 			--i;
 			LYXERR(Debug::DEBUG, "fixIfBroken(): inset changed");