diff --git a/Makefile b/Makefile
index 451a944a1720671097bc4bcfc757e3751ce2d6a1..e366a35d2c29ba3dcbcd95fda9657a0570cd904e 100644
--- a/Makefile
+++ b/Makefile
@@ -29,7 +29,7 @@ PROGS := coalg coalgcompare
 LIBS := unix str
 SOURCESMLI := $(wildcard *.mli)
 SOURCESML := $(wildcard *.ml)
-INCS ?= -I/usr/include -I/usr/lib/ocaml -I.
+INCS ?= -I/usr/include -I/usr/lib/ocaml -I/usr/local/lib/ocaml -I.
 CXXFLAGS += -Wall -Werror $(INCS)
 LDXX ?= g++