diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0da09c8..339cd0b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -27,7 +27,7 @@ jobs:
 
     strategy:
       matrix:
-        rust_version: [stable, "1.53.0"]
+        rust_version: [stable, "1.58.0"]
 
     steps:
     - uses: actions/checkout@v2
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6704ae0..ba77e12 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,8 @@
 # Foreman Changelog
 
+## Unreleased
+- Errors when duplicate tools are defined in `foreman.toml` ([#65](https://github.com/Roblox/foreman/pull/65))
+
 ## 1.0.6 (2022-09-28)
 
 - Support `macos-aarch64` as an artifact name for Apple Silicon (arm64) binaries ([#60](https://github.com/Roblox/foreman/pull/60))
diff --git a/src/config.rs b/src/config.rs
index e9cdf15..1cb71bf 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -1,7 +1,14 @@
-use std::{collections::BTreeMap, env, fmt};
+use std::{
+    collections::BTreeMap,
+    env, fmt,
+    ops::{Deref, DerefMut},
+};
 
 use semver::VersionReq;
-use serde::{Deserialize, Serialize};
+use serde::{
+    de::{self, MapAccess, Visitor},
+    Deserialize, Serialize,
+};
 
 use crate::{
     ci_string::CiString, error::ForemanError, fs, paths::ForemanPaths, tool_provider::Provider,
@@ -67,20 +74,43 @@ impl fmt::Display for ToolSpec {
     }
 }
 
+#[derive(Debug, Serialize)]
+pub struct ConfigFileTools(BTreeMap<String, ToolSpec>);
+
+impl ConfigFileTools {
+    pub fn new() -> ConfigFileTools {
+        Self(BTreeMap::new())
+    }
+}
+
+impl Deref for ConfigFileTools {
+    type Target = BTreeMap<String, ToolSpec>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl DerefMut for ConfigFileTools {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
 #[derive(Debug, Serialize, Deserialize)]
 pub struct ConfigFile {
-    pub tools: BTreeMap<String, ToolSpec>,
+    pub tools: ConfigFileTools,
 }
 
 impl ConfigFile {
     pub fn new() -> Self {
         Self {
-            tools: BTreeMap::new(),
+            tools: ConfigFileTools::new(),
         }
     }
 
     fn fill_from(&mut self, other: ConfigFile) {
-        for (tool_name, tool_source) in other.tools {
+        for (tool_name, tool_source) in other.tools.0 {
             self.tools.entry(tool_name).or_insert(tool_source);
         }
     }
@@ -141,6 +171,48 @@ impl fmt::Display for ConfigFile {
     }
 }
 
+struct ConfigFileVisitor;
+
+impl<'de> Visitor<'de> for ConfigFileVisitor {
+    type Value = ConfigFileTools;
+
+    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("a map with non-duplicate keys")
+    }
+
+    fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
+    where
+        A: MapAccess<'de>,
+    {
+        let mut tools = BTreeMap::new();
+
+        while let Some((key, value)) = map.next_entry()? {
+            if tools.contains_key(&key) {
+                // item already existed inside the config
+                // throw an error as this is unlikely to be the users intention
+                return Err(de::Error::custom(format!(
+                    "duplicate tool name `{key}` found"
+                )));
+            }
+
+            tools.insert(key, value);
+        }
+
+        Ok(ConfigFileTools(tools))
+    }
+}
+
+impl<'de> Deserialize<'de> for ConfigFileTools {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        let tools = deserializer.deserialize_map(ConfigFileVisitor)?;
+
+        Ok(tools)
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;
@@ -189,6 +261,44 @@ mod test {
                     .unwrap();
             assert_eq!(gitlab, new_gitlab("user/repo", version("0.1.0")));
         }
+
+        #[test]
+        fn duplicate_tools() {
+            let err = toml::from_str::<ConfigFileTools>(
+                r#"tool = { github = "user/repo", version = "0.1.0" }
+			tool = { github = "user2/repo2", version = "0.2.0" }"#,
+            )
+            .unwrap_err();
+
+            assert_eq!(
+                err.to_string(),
+                "duplicate tool name `tool` found at line 1 column 1"
+            );
+
+            let err = toml::from_str::<ConfigFileTools>(
+                r#"tool_a = { github = "user/a", version = "0.1.0" }
+			tool_b = { github = "user/b", version = "0.2.0" }
+			tool_a = { gitlab = "user/c", version = "0.3.0" }"#,
+            )
+            .unwrap_err();
+
+            assert_eq!(
+                err.to_string(),
+                "duplicate tool name `tool_a` found at line 1 column 1"
+            );
+
+            let err = toml::from_str::<ConfigFileTools>(
+                r#"tool_b = { github = "user/b", version = "0.1.0" }
+			tool_a = { github = "user/a", version = "0.2.0" }
+			tool_a = { gitlab = "user/c", version = "0.3.0" }"#,
+            )
+            .unwrap_err();
+
+            assert_eq!(
+                err.to_string(),
+                "duplicate tool name `tool_a` found at line 1 column 1"
+            );
+        }
     }
 
     #[test]