diff --git a/Makefile b/Makefile
index b5f718c..52b9eeb 100644
--- a/Makefile
+++ b/Makefile
@@ -7,8 +7,8 @@ RESULT = cpdf
 ANNOTATE = true
 PACKS = camlpdf
 
-OCAMLNCFLAGS = -g -w -3 -annot
-OCAMLBCFLAGS = -g -w -3 -annot
+OCAMLNCFLAGS = -g -unsafe-string -w -3 -annot
+OCAMLBCFLAGS = -g -unsafe-string -w -3 -annot
 OCAMLLDFLAGS = -g
 
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