https://forge.ocamlcore.org/tracker/index.php?func=detail&aid=1201&group_id=278&atid=1189

Index: camldbm-1.0/Makefile
===================================================================
--- camldbm-1.0.orig/Makefile
+++ camldbm-1.0/Makefile
@@ -51,7 +51,7 @@ libcamldbm.$(A): cldbm.$(O)
 	$(OCAMLOPT) -c $(COMPFLAGS) $<
 
 .c.$(O):
-	$(OCAMLC) -c -ccopt "$(DBM_INCLUDE)" -ccopt "$(DBM_DEFINES)" $<
+	$(OCAMLC) -c -ccopt "$(DBM_INCLUDES)" -ccopt "$(DBM_DEFINES)" $<
 
 depend:
 	$(OCAMLDEP) *.ml *.mli > .depend