diff --git a/irmin-chunk.opam b/irmin-chunk.opam
index 756ec81ad0..887190cfa5 100644
--- a/irmin-chunk.opam
+++ b/irmin-chunk.opam
@@ -13,7 +13,7 @@ build: [
 ]
 
 depends: [
-  "ocaml"      {>= "4.02.3"}
+  "ocaml"      {>= "5.1.0"}
   "dune"       {>= "3.5.0"}
   "irmin"      {= version}
   "fmt"
diff --git a/irmin-cli.opam b/irmin-cli.opam
index 6a798562e2..b469c698bf 100644
--- a/irmin-cli.opam
+++ b/irmin-cli.opam
@@ -16,7 +16,7 @@ build: [
 available: arch != "arm32" & arch != "x86_32"
 
 depends: [
-  "ocaml"         {>= "4.01.0"}
+  "ocaml"         {>= "5.1.0"}
   "dune"          {>= "3.5.0"}
   "irmin"         {= version}
   "irmin-git"     {= version}
diff --git a/irmin-client.opam b/irmin-client.opam
index 696e617c27..77ac627658 100644
--- a/irmin-client.opam
+++ b/irmin-client.opam
@@ -8,7 +8,7 @@ doc: "https://irmin.org"
 dev-repo: "git+ssh://github.com/mirage/irmin"
 bug-reports: "https://github.com/mirage/irmin/issues"
 depends: [
-  "ocaml" {>= "4.08.0"}
+  "ocaml" {>= "5.1.0"}
   "dune" {>= "3.5.0"}
   "irmin-server" {= version}
   "irmin-cli" {= version}
diff --git a/irmin-containers.opam b/irmin-containers.opam
index 500d4d5b15..088baf7a56 100644
--- a/irmin-containers.opam
+++ b/irmin-containers.opam
@@ -14,7 +14,7 @@ build: [
 ]
 
 depends: [
-  "ocaml"        {>= "4.03.0"}
+  "ocaml"        {>= "5.1.0"}
   "dune"         {>= "3.5.0"}
   "irmin"        {= version}
   "irmin-fs"     {= version}
diff --git a/irmin-fs.opam b/irmin-fs.opam
index 8cc535640c..900563fff4 100644
--- a/irmin-fs.opam
+++ b/irmin-fs.opam
@@ -14,7 +14,7 @@ build: [
 ]
 
 depends: [
-  "ocaml"      {>= "4.03.0"}
+  "ocaml"      {>= "5.1.0"}
   "dune"       {>= "3.5.0"}
   "irmin"      {= version}
   "astring"
diff --git a/irmin-git.opam b/irmin-git.opam
index 6f0f202c22..1fef98b12f 100644
--- a/irmin-git.opam
+++ b/irmin-git.opam
@@ -15,7 +15,7 @@ build: [
 ]
 
 depends: [
-  "ocaml"      {>= "4.02.3"}
+  "ocaml"      {>= "5.1.0"}
   "dune"       {>= "3.5.0"}
   "irmin"      {= version}
   "ppx_irmin"  {= version}
diff --git a/irmin-graphql.opam b/irmin-graphql.opam
index 7b1533bf46..2b61f77202 100644
--- a/irmin-graphql.opam
+++ b/irmin-graphql.opam
@@ -14,7 +14,7 @@ build: [
 ]
 
 depends: [
-  "ocaml"          {>= "4.03.0"}
+  "ocaml"          {>= "5.1.0"}
   "dune"           {>= "3.5.0"}
   "irmin"          {= version}
   "graphql"        {>= "0.14.0"}
diff --git a/irmin-http.opam b/irmin-http.opam
index 541cda4805..47edc91aff 100644
--- a/irmin-http.opam
+++ b/irmin-http.opam
@@ -14,7 +14,7 @@ build: [
 ]
 
 depends: [
-  "ocaml"           {>= "4.02.3"}
+  "ocaml"           {>= "5.1.0"}
   "dune"            {>= "3.5.0"}
   "crunch"          {>= "2.2.0"}
   "webmachine"      {>= "0.6.0"}
diff --git a/irmin-pack-tools.opam b/irmin-pack-tools.opam
index 1589e1f5a8..ff059d2829 100644
--- a/irmin-pack-tools.opam
+++ b/irmin-pack-tools.opam
@@ -16,7 +16,7 @@ build: [
 available: arch != "arm32" & arch != "x86_32"
 
 depends: [
-  "ocaml"       {>= "4.01.0"}
+  "ocaml"       {>= "5.1.0"}
   "dune"        {>= "3.5.0"}
   "irmin-tezos" {= version}
   "irmin-pack"  {= version}
diff --git a/irmin-pack.opam b/irmin-pack.opam
index a7af890189..9d580c6144 100644
--- a/irmin-pack.opam
+++ b/irmin-pack.opam
@@ -13,7 +13,7 @@ build: [
 ]
 
 depends: [
-  "ocaml"        {>= "4.12.0"}
+  "ocaml"        {>= "5.1.0"}
   "dune"         {>= "3.5.0"}
   "irmin"        {= version}
   "ppx_irmin"    {= version}
diff --git a/irmin-server.opam b/irmin-server.opam
index 5df0018e93..6c2d21674c 100644
--- a/irmin-server.opam
+++ b/irmin-server.opam
@@ -8,7 +8,7 @@ doc: "https://irmin.org"
 dev-repo: "git+ssh://github.com/mirage/irmin"
 bug-reports: "https://github.com/mirage/irmin/issues"
 depends: [
-  "ocaml" {>= "4.08.0"}
+  "ocaml" {>= "5.1.0"}
   "dune" {>= "3.5.0"}
   "optint" {>= "0.1.0"}
   "irmin" {= version}
diff --git a/irmin-test.opam b/irmin-test.opam
index 7955c7b3e4..994e735074 100644
--- a/irmin-test.opam
+++ b/irmin-test.opam
@@ -15,7 +15,7 @@ build: [
 depends: [
   "irmin"        {= version}
   "ppx_irmin"    {= version}
-  "ocaml"        {>= "4.02.3"}
+  "ocaml"        {>= "5.1.0"}
   "dune"         {>= "3.5.0"}
   "mtime"        {>= "2.0.0"}
   "astring"
diff --git a/irmin.opam b/irmin.opam
index 5619596f81..73da72ab39 100644
--- a/irmin.opam
+++ b/irmin.opam
@@ -14,7 +14,7 @@ build: [
 ]
 
 depends: [
-  "ocaml"   {>= "4.08.0"}
+  "ocaml"   {>= "5.1.0"}
   "dune"    {>= "3.5.0"}
   "repr"    {>= "0.6.0"}
   "fmt"     {>= "0.8.5"}