diff --git a/Sources/ApodiniContext/Context.swift b/Sources/ApodiniContext/Context.swift
index 5871275..ff45013 100644
--- a/Sources/ApodiniContext/Context.swift
+++ b/Sources/ApodiniContext/Context.swift
@@ -11,9 +11,12 @@ import OrderedCollections
 
 private class ContextBox {
     var entries: [ObjectIdentifier: StoredContextValue]
+    /// Mapping from ``CodableContextKey/identifier`` to base64 encoded data
+    var decodedEntries: [String: String]
 
-    init(_ entries: [ObjectIdentifier: StoredContextValue]) {
+    init(_ entries: [ObjectIdentifier: StoredContextValue], _ decodedEntries: [String: String]) {
         self.entries = entries
+        self.decodedEntries = decodedEntries
     }
 }
 
@@ -26,15 +29,17 @@ struct StoredContextValue {
 /// A `Context` holds a collection of values for predefined `ContextKey`s or `OptionalContextKey`s.
 public struct Context: ContextKeyRetrievable {
     private var boxedEntries: ContextBox
+
     private var entries: [ObjectIdentifier: StoredContextValue] {
         boxedEntries.entries
     }
-    /// Mapping from ``CodableContextKey/identifier`` to base64 encoded data
-    private let decodedEntries: [String: String]
+
+    private var decodedEntries: [String: String] {
+        boxedEntries.decodedEntries
+    }
 
     init(_ entries: [ObjectIdentifier: StoredContextValue] = [:], _ decodedEntries: [String: String] = [:]) {
-        self.boxedEntries = ContextBox(entries)
-        self.decodedEntries = decodedEntries
+        self.boxedEntries = ContextBox(entries, decodedEntries)
     }
 
     /// Create a new empty ``Context``.
@@ -97,14 +102,21 @@ public struct Context: ContextKeyRetrievable {
         precondition(entries[key] == nil || allowOverwrite, "Cannot overwrite existing ContextKey entry with `unsafeAdd`: \(C.self): \(value)")
         if let codableContextKey = contextKey as? AnyCodableContextKey.Type {
             // we need to prevent this. as Otherwise we would need to handle merging this stuff which get really complex
-            precondition(decodedEntries[codableContextKey.identifier] == nil, "Cannot overwrite existing CodableContextKey entry with `unsafeAdd`: \(C.self): \(value)")
+            precondition(
+                decodedEntries[codableContextKey.identifier] == nil || allowOverwrite,
+                "Cannot overwrite existing CodableContextKey entry with `unsafeAdd`: \(C.self): \(value)"
+            )
+
+            // if we reach this point, either the key doesn't exist or `allowOverwrite` was turned on
+            // and we need to remove the existing entry in order to properly overwrite everything
+            boxedEntries.decodedEntries.removeValue(forKey: codableContextKey.identifier)
         }
 
         boxedEntries.entries[key] = StoredContextValue(key: contextKey, value: value)
     }
 
     private func checkForDecodedEntries<Key: CodableContextKey>(for key: Key.Type = Key.self) -> Key.Value? {
-        guard let dataValue = decodedEntries[Key.identifier] else {
+        guard let dataValue = boxedEntries.decodedEntries.removeValue(forKey: Key.identifier) else {
             return nil
         }
 
@@ -140,15 +152,13 @@ extension Context: Codable {
     public init(from decoder: Decoder) throws {
         let container = try decoder.container(keyedBy: StringContextKey.self)
 
-        self.boxedEntries = ContextBox([:])
-
         var decodedEntries: [String: String] = [:]
 
         for key in container.allKeys {
             decodedEntries[key.stringValue] = try container.decode(String.self, forKey: key)
         }
 
-        self.decodedEntries = decodedEntries
+        self.boxedEntries = ContextBox([:], decodedEntries)
     }
 
     public func encode(to encoder: Encoder) throws {
diff --git a/Tests/ApodiniContextTests/ContextKeyTests.swift b/Tests/ApodiniContextTests/ContextKeyTests.swift
index 1e16a20..9eb64b4 100644
--- a/Tests/ApodiniContextTests/ContextKeyTests.swift
+++ b/Tests/ApodiniContextTests/ContextKeyTests.swift
@@ -118,7 +118,7 @@ class ContextKeyTests: XCTestCase {
         XCTAssertEqual(decodedContext.get(valueFor: CodableArrayStringContextKey.self), ["Hello Sun"])
     }
 
-    func testUnsafeAddAllowingOverwrite() {
+    func testUnsafeAddAllowingOverwrite() throws {
         struct CodableStringContextKey: CodableContextKey {
             typealias Value = String
         }
@@ -129,5 +129,20 @@ class ContextKeyTests: XCTestCase {
         XCTAssertEqual(context.get(valueFor: CodableStringContextKey.self), "Hello World")
         context.unsafeAdd(CodableStringContextKey.self, value: "Hello Mars", allowOverwrite: true)
         XCTAssertEqual(context.get(valueFor: CodableStringContextKey.self), "Hello Mars")
+
+        let encoder = FineJSONEncoder()
+        encoder.jsonSerializeOptions = .init(isPrettyPrint: false)
+        let decoder = FineJSONDecoder()
+
+        let encodedContext = try encoder.encode(context)
+        XCTAssertEqual(
+            String(data: encodedContext, encoding: .utf8),
+            "{\"CodableStringContextKey\":\"IkhlbGxvIE1hcnMi\"}"
+        )
+
+        let decodedContext = try decoder.decode(Context.self, from: encodedContext)
+
+        decodedContext.unsafeAdd(CodableStringContextKey.self, value: "Hello Saturn", allowOverwrite: true)
+        XCTAssertEqual(decodedContext.get(valueFor: CodableStringContextKey.self), "Hello Saturn")
     }
 }