diff --git a/src/support/docstream.cpp b/src/support/docstream.cpp
index 21f1f3a58e..bd2d010ff6 100644
--- a/src/support/docstream.cpp
+++ b/src/support/docstream.cpp
@@ -122,6 +122,7 @@ protected:
 		// of the input buffer in order to circumvent an iconv bug.
 		if (from_new) {
 			--to_next;
+			--from_next;
 			from_next = from_old + (from_next - from);
 			from = from_old;
 			delete[] from_new;