diff --git a/README.md b/README.md
index 3b0a270a..33a5d3ab 100644
--- a/README.md
+++ b/README.md
@@ -27,8 +27,8 @@ The name of this repository is a pun on two meanings of "time to": "how much tim
 | C (optimized, 16 threads)   | 5ms       | 249  |
 | squiggle.c                  | 37ms      | 54   | 
 | Nim                         | 38ms      | 84   |
-| OCaml                       | 42ms      | 112  |
 | Lua (LuaJIT)                | 68ms      | 82   |
+| OCaml (flambda mode)        | 245ms     | 112  |
 | Lua                         | 278ms     | 82   |
 | C (naïve implementation)    | 292ms     | 149  |
 | Javascript (NodeJS)         | 732ms     | 69   |
diff --git a/nim/samples b/nim/samples
index 17b5420a..372f704e 100755
Binary files a/nim/samples and b/nim/samples differ
diff --git a/ocaml/makefile b/ocaml/makefile
index 2f5407c3..78edcbc1 100644
--- a/ocaml/makefile
+++ b/ocaml/makefile
@@ -1,18 +1,30 @@
 # Compiler
-CC=ocamlopt
+OC=ocamlopt
 # ocamlopt: platform-specific, faster
 # ocamlc: platform-independent intermediate representation, run with ocamlrun
+FAST=-O3 -unsafe # install flambda with opam
 
-# Main file
 SRC=samples.ml
 OUT=./out/samples
 
 build: $(SRC)
-	$(CC) $(SRC) -o $(OUT)
+	$(OC) $(SRC) -o $(OUT)
 	mv samples.cmi samples.cmx samples.o ./out/
 
 run:
 	$(OUT)
 
+fast:
+	$(OC) $(FAST) $(SRC) -o $(OUT)
+	mv samples.cmi samples.cmx samples.o ./out/
+
 time:
 	bash -c "time $(OUT)"
+
+switch-opam-fast:
+	opam switch create 4.11.2+flambda 
+	eval $(opam env)
+
+switch-opam-5.1.0:
+	opam switch create 5.1.0 
+	eval $(opam env)
diff --git a/ocaml/out/samples b/ocaml/out/samples
index f23bec4e..b0583db9 100755
Binary files a/ocaml/out/samples and b/ocaml/out/samples differ
diff --git a/ocaml/out/samples.cmi b/ocaml/out/samples.cmi
index 67a0c682..1e08142f 100644
Binary files a/ocaml/out/samples.cmi and b/ocaml/out/samples.cmi differ
diff --git a/ocaml/out/samples.cmx b/ocaml/out/samples.cmx
index 4065573b..9c64b036 100644
Binary files a/ocaml/out/samples.cmx and b/ocaml/out/samples.cmx differ
diff --git a/ocaml/out/samples.o b/ocaml/out/samples.o
index df7a9bd0..bb7fa6ad 100644
Binary files a/ocaml/out/samples.o and b/ocaml/out/samples.o differ
diff --git a/time.txt b/time.txt
index 6c4cdcbc..74d978df 100644
--- a/time.txt
+++ b/time.txt
@@ -140,14 +140,12 @@ Time using 1 thread: 37.60ms
 
 ## squiggle.ml
 
-— make build && make time
-ocamlopt samples.ml -o ./out/samples
+— make fast && make time
+ocamlopt -O3 -unsafe  samples.ml -o ./out/samples
 mv samples.cmi samples.cmx samples.o ./out/
 bash -c "time ./out/samples"
-Mean: 0.884629
+Mean: 0.886498
 
-real    0m0.425s
-user    0m0.393s
-sys     0m0.032s
- 
-42ms
+real    0m0.245s
+user    0m0.232s
+sys     0m0.012s