diff --git a/src/server/actors/repo/config.rs b/src/server/actors/repo/config.rs
index dbf08be3..604c2542 100644
--- a/src/server/actors/repo/config.rs
+++ b/src/server/actors/repo/config.rs
@@ -11,7 +11,7 @@ use super::{LoadedConfig, RepoActor};
 
 pub async fn load(details: RepoDetails, addr: Addr<RepoActor>, net: Network) {
     let config = match details.forge.forge_type {
-        ForgeType::ForgeJo => forge::forgejo::config::load(details, &net).await,
+        ForgeType::ForgeJo => forge::forgejo::config::load(&details, &net).await,
     };
     match config {
         Ok(config) => addr.do_send(LoadedConfig(config)),
diff --git a/src/server/config.rs b/src/server/config.rs
index 420aa73a..a3de9aa8 100644
--- a/src/server/config.rs
+++ b/src/server/config.rs
@@ -34,6 +34,10 @@ impl RepoConfig {
     pub(crate) fn load(toml: &str) -> Result<Self, OneOf<(toml::de::Error,)>> {
         toml::from_str(toml).map_err(OneOf::new)
     }
+
+    pub(crate) const fn branches(&self) -> &RepoBranches {
+        &self.branches
+    }
 }
 impl Display for RepoConfig {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
@@ -46,6 +50,19 @@ pub struct RepoBranches {
     next: String,
     dev: String,
 }
+impl RepoBranches {
+    pub fn main(&self) -> BranchName {
+        BranchName(self.main.clone())
+    }
+
+    pub fn next(&self) -> BranchName {
+        BranchName(self.next.clone())
+    }
+
+    pub fn dev(&self) -> BranchName {
+        BranchName(self.dev.clone())
+    }
+}
 impl Display for RepoBranches {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         write!(f, "{:?}", self)
diff --git a/src/server/forge/forgejo/config.rs b/src/server/forge/forgejo/config.rs
index 3149fb5c..f2c076fb 100644
--- a/src/server/forge/forgejo/config.rs
+++ b/src/server/forge/forgejo/config.rs
@@ -3,26 +3,37 @@ use kxio::network::{self, Network};
 use terrors::OneOf;
 use tracing::{error, info};
 
-use crate::server::config::{RepoConfig, RepoDetails};
+use crate::server::config::{BranchName, RepoConfig, RepoDetails};
+
+#[derive(Debug)]
+pub struct RepoConfigFileNotFound;
+#[derive(Debug)]
+pub struct RepoConfigIsNotFile;
+#[derive(Debug)]
+pub struct RepoConfigDecodeError;
+#[derive(Debug)]
+pub struct RepoConfigParseError;
+#[derive(Debug)]
+pub struct RepoConfigUnknownError(pub network::StatusCode);
+
+type RepoConfigLoadErrors = (
+    RepoConfigFileNotFound,
+    RepoConfigIsNotFile,
+    RepoConfigDecodeError,
+    RepoConfigParseError,
+    RepoConfigUnknownError,
+    RepoConfigBranchNotFound,
+);
 
 pub async fn load(
-    details: RepoDetails,
+    details: &RepoDetails,
     net: &Network,
-) -> Result<
-    RepoConfig,
-    OneOf<(
-        RepoConfigFileNotFound,
-        RepoConfigIsNotFile,
-        RepoConfigDecodeError,
-        RepoConfigParseError,
-        RepoConfigUnknownError,
-    )>,
-> {
-    let hostname = details.forge.hostname;
-    let path = details.repo;
+) -> Result<RepoConfig, OneOf<RepoConfigLoadErrors>> {
+    let hostname = &details.forge.hostname;
+    let path = &details.repo;
     let filepath = ".git-next.toml";
-    let branch = details.branch;
-    let token = details.forge.token;
+    let branch = &details.branch;
+    let token = &details.forge.token;
     let url = network::NetUrl::new(format!(
         "https://{hostname}/api/v1/repos/{path}/contents/{filepath}?ref={branch}&token={token}"
     ));
@@ -49,7 +60,7 @@ pub async fn load(
         )),
     })?;
     let status = response.status_code();
-    match response.response_body() {
+    let config = match response.response_body() {
         Some(body) => {
             // we need to decode (see encoding field) the value of 'content' from the response
             match body.content_type {
@@ -61,7 +72,11 @@ pub async fn load(
             error!(%status, "Failed to fetch repo config file");
             Err(OneOf::new(RepoConfigUnknownError(status)))
         }
-    }
+    }?;
+    let config = validate(details, config, net)
+        .await
+        .map_err(OneOf::broaden)?;
+    Ok(config)
 }
 
 fn decode_config(
@@ -81,17 +96,6 @@ fn decode_config(
     }
 }
 
-#[derive(Debug)]
-pub struct RepoConfigFileNotFound;
-#[derive(Debug)]
-pub struct RepoConfigIsNotFile;
-#[derive(Debug)]
-pub struct RepoConfigDecodeError;
-#[derive(Debug)]
-pub struct RepoConfigParseError;
-#[derive(Debug)]
-pub struct RepoConfigUnknownError(pub network::StatusCode);
-
 #[derive(Clone, Debug, serde::Deserialize)]
 struct ForgeContentsResponse {
     #[serde(rename = "type")]
@@ -110,3 +114,77 @@ enum ForgeContentsType {
     #[serde(rename = "submodule")]
     Submodule,
 }
+
+#[derive(Debug)]
+pub struct RepoConfigBranchNotFound(pub BranchName);
+
+type RepoConfigValidateErrors = (RepoConfigBranchNotFound, RepoConfigUnknownError);
+
+pub async fn validate(
+    details: &RepoDetails,
+    config: RepoConfig,
+    net: &Network,
+) -> Result<RepoConfig, OneOf<RepoConfigValidateErrors>> {
+    let hostname = &details.forge.hostname;
+    let path = &details.repo;
+    let token = &details.forge.token;
+    let url = network::NetUrl::new(format!(
+        "https://{hostname}/api/v1/repos/{path}/branches?token={token}"
+    ));
+
+    info!(%url, "Listing branches");
+    let request = network::NetRequest::new(
+        network::RequestMethod::Get,
+        url,
+        network::NetRequestHeaders::new(),
+        network::RequestBody::None,
+        network::ResponseType::Json,
+        None,
+        network::NetRequestLogging::Both,
+    );
+    let result = net.get::<BranchList>(request).await;
+    let response = result.map_err(|e| {
+        error!(?e, "Failed to list branches");
+        OneOf::new(RepoConfigUnknownError(
+            network::StatusCode::INTERNAL_SERVER_ERROR,
+        ))
+    })?;
+    let branches = response.response_body().unwrap_or_default();
+    if !branches
+        .iter()
+        .any(|branch| branch.name() == config.branches().main())
+    {
+        return Err(OneOf::new(RepoConfigBranchNotFound(
+            config.branches().main(),
+        )));
+    }
+    if !branches
+        .iter()
+        .any(|branch| branch.name() == config.branches().next())
+    {
+        return Err(OneOf::new(RepoConfigBranchNotFound(
+            config.branches().next(),
+        )));
+    }
+    if !branches
+        .iter()
+        .any(|branch| branch.name() == config.branches().dev())
+    {
+        return Err(OneOf::new(RepoConfigBranchNotFound(
+            config.branches().dev(),
+        )));
+    }
+    Ok(config)
+}
+
+type BranchList = Vec<Branch>;
+
+#[derive(Debug, serde::Deserialize)]
+struct Branch {
+    name: String,
+}
+impl Branch {
+    fn name(&self) -> BranchName {
+        BranchName(self.name.clone())
+    }
+}