diff --git a/serde/Cargo.toml b/serde/Cargo.toml
index c33ff331..4225585e 100644
--- a/serde/Cargo.toml
+++ b/serde/Cargo.toml
@@ -11,6 +11,8 @@ readme = "../README.md"
 keywords = ["serde", "serialization"]
 include = ["Cargo.toml", "src/**/*.rs"]
 
+publish = false # this branch contains breaking changes for 0.9
+
 [features]
 default = ["std"]
 
diff --git a/serde_codegen/Cargo.toml b/serde_codegen/Cargo.toml
index ca8b7581..39261519 100644
--- a/serde_codegen/Cargo.toml
+++ b/serde_codegen/Cargo.toml
@@ -10,6 +10,8 @@ documentation = "https://serde.rs/codegen.html"
 keywords = ["serde", "serialization"]
 include = ["Cargo.toml", "src/**/*.rs"]
 
+publish = false # this branch contains breaking changes for 0.9
+
 [features]
 default = ["with-syntex"]
 unstable = []
diff --git a/serde_codegen_internals/Cargo.toml b/serde_codegen_internals/Cargo.toml
index f03cacd8..f98310f2 100644
--- a/serde_codegen_internals/Cargo.toml
+++ b/serde_codegen_internals/Cargo.toml
@@ -10,6 +10,8 @@ documentation = "https://docs.serde.rs/serde_codegen_internals/"
 keywords = ["serde", "serialization"]
 include = ["Cargo.toml", "src/**/*.rs"]
 
+publish = false # this branch contains breaking changes for 0.9
+
 [features]
 unstable-testing = ["clippy"]
 
diff --git a/serde_derive/Cargo.toml b/serde_derive/Cargo.toml
index 053732e0..2765340b 100644
--- a/serde_derive/Cargo.toml
+++ b/serde_derive/Cargo.toml
@@ -10,6 +10,8 @@ documentation = "https://serde.rs/codegen.html"
 keywords = ["serde", "serialization"]
 include = ["Cargo.toml", "src/**/*.rs"]
 
+publish = false # this branch contains breaking changes for 0.9
+
 [lib]
 name = "serde_derive"
 proc-macro = true
diff --git a/serde_test/Cargo.toml b/serde_test/Cargo.toml
index 5e39bbce..a17bf62d 100644
--- a/serde_test/Cargo.toml
+++ b/serde_test/Cargo.toml
@@ -11,5 +11,7 @@ readme = "../README.md"
 keywords = ["serde", "serialization"]
 include = ["Cargo.toml", "src/**/*.rs"]
 
+publish = false # this branch contains breaking changes for 0.9
+
 [dependencies]
 serde = { version = "0.8.21", path = "../serde" }