diff --git a/Sources/OpenAPIRuntime/URICoder/Common/URICodeCodingKey.swift b/Sources/OpenAPIRuntime/URICoder/Common/URICodeCodingKey.swift
index 5a86dc11..b2b665b3 100644
--- a/Sources/OpenAPIRuntime/URICoder/Common/URICodeCodingKey.swift
+++ b/Sources/OpenAPIRuntime/URICoder/Common/URICodeCodingKey.swift
@@ -27,13 +27,6 @@ struct URICoderCodingKey {
     /// The value to use in an integer-indexed collection (e.g. an int-keyed
     /// dictionary).
     var intValue: Int?
-
-    /// Creates a new key with the same string and int value as the provided key.
-    /// - Parameter key: The key whose values to copy.
-    init(_ key: some CodingKey) {
-        self.stringValue = key.stringValue
-        self.intValue = key.intValue
-    }
 }
 
 extension URICoderCodingKey: CodingKey {
diff --git a/Sources/OpenAPIRuntime/URICoder/Decoding/URIValueFromNodeDecoder+Keyed.swift b/Sources/OpenAPIRuntime/URICoder/Decoding/URIValueFromNodeDecoder+Keyed.swift
index c1ac27d7..fedf39e3 100644
--- a/Sources/OpenAPIRuntime/URICoder/Decoding/URIValueFromNodeDecoder+Keyed.swift
+++ b/Sources/OpenAPIRuntime/URICoder/Decoding/URIValueFromNodeDecoder+Keyed.swift
@@ -154,7 +154,9 @@ extension URIKeyedDecodingContainer: KeyedDecodingContainerProtocol {
         case is UInt64.Type: return try decode(UInt64.self, forKey: key) as! T
         case is Date.Type: return try decoder.dateTranscoder.decode(String(_decodeValue(forKey: key))) as! T
         default:
-            decoder.push(.init(key))
+            // Only push the string value of the key, as keys e.g. in a string-keyed
+            // dictionary can have an integer value that doesn't represent an array index.
+            decoder.push(.init(stringValue: key.stringValue))
             defer { decoder.pop() }
             return try type.init(from: decoder)
         }
diff --git a/Sources/OpenAPIRuntime/URICoder/Encoding/URIValueToNodeEncoder+Keyed.swift b/Sources/OpenAPIRuntime/URICoder/Encoding/URIValueToNodeEncoder+Keyed.swift
index dc4c572b..4e3bac26 100644
--- a/Sources/OpenAPIRuntime/URICoder/Encoding/URIValueToNodeEncoder+Keyed.swift
+++ b/Sources/OpenAPIRuntime/URICoder/Encoding/URIValueToNodeEncoder+Keyed.swift
@@ -29,12 +29,15 @@ extension URIKeyedEncodingContainer {
 
     /// Inserts the provided node into the underlying dictionary at
     /// the provided key.
+    ///
+    /// Only the string value of the key is used, as keys e.g. in a string-keyed
+    /// dictionary can have an integer value that doesn't represent an array index.
     /// - Parameters:
     ///   - node: The child node to insert.
     ///   - key: The key for the child node.
     /// - Throws: An error if inserting the child node into the underlying dictionary at the provided key fails.
     private func _insertValue(_ node: URIEncodedNode, atKey key: Key) throws {
-        try encoder.currentStackEntry.storage.insert(node, atKey: key)
+        try encoder.currentStackEntry.storage.insert(node, atKey: URICoderCodingKey(stringValue: key.stringValue))
     }
 
     /// Inserts the provided primitive value into the underlying dictionary at
@@ -126,7 +129,7 @@ extension URIKeyedEncodingContainer: KeyedEncodingContainerProtocol {
         case let value as Bool: try encode(value, forKey: key)
         case let value as Date: try _insertValue(.date(value), atKey: key)
         default:
-            encoder.push(key: .init(key), newStorage: .unset)
+            encoder.push(key: .init(stringValue: key.stringValue), newStorage: .unset)
             try value.encode(to: encoder)
             try encoder.pop()
         }
diff --git a/Tests/OpenAPIRuntimeTests/URICoder/Decoder/Test_URIDecoder.swift b/Tests/OpenAPIRuntimeTests/URICoder/Decoder/Test_URIDecoder.swift
index a0d9079b..e5590fcc 100644
--- a/Tests/OpenAPIRuntimeTests/URICoder/Decoder/Test_URIDecoder.swift
+++ b/Tests/OpenAPIRuntimeTests/URICoder/Decoder/Test_URIDecoder.swift
@@ -119,6 +119,29 @@ final class Test_URIDecoder: Test_Runtime {
         }
     }
 
+    func testDecoding_freeformObjectWithNumericKey() throws {
+        let decoder = URIDecoder(configuration: .formExplode)
+        let decodedValue = try decoder.decode(OpenAPIObjectContainer.self, forKey: "filter", from: "5=x&name=y")
+        XCTAssertEqual(decodedValue, try .init(unvalidatedValue: ["5": "x", "name": "y"]))
+    }
+
+    func testDecoding_dictionaryOfEnumsWithNumericKey() throws {
+        enum Color: String, Decodable, Equatable { case red }
+        _test(
+            ["7": Color.red],
+            forKey: "keys",
+            from: .init(
+                formExplode: "7=red",
+                formUnexplode: "keys=7,red",
+                simpleExplode: "7=red",
+                simpleUnexplode: "7,red",
+                formDataExplode: "7=red",
+                formDataUnexplode: "keys=7,red",
+                deepObjectExplode: "keys%5B7%5D=red"
+            )
+        )
+    }
+
     func testDecoding_rootValue() throws {
         let decoder = URIDecoder(configuration: .formDataExplode)
         do {
diff --git a/Tests/OpenAPIRuntimeTests/URICoder/Test_URICodingRoundtrip.swift b/Tests/OpenAPIRuntimeTests/URICoder/Test_URICodingRoundtrip.swift
index 9c17d4e4..ab5a7c00 100644
--- a/Tests/OpenAPIRuntimeTests/URICoder/Test_URICodingRoundtrip.swift
+++ b/Tests/OpenAPIRuntimeTests/URICoder/Test_URICodingRoundtrip.swift
@@ -341,6 +341,64 @@ final class Test_URICodingRoundtrip: Test_Runtime {
             )
         )
 
+        // A dictionary with a numeric-looking key, which must not be treated as an array index.
+        try _test(
+            ["5": "x"],
+            key: "keys",
+            .init(
+                formExplode: "5=x",
+                formUnexplode: "keys=5,x",
+                simpleExplode: "5=x",
+                simpleUnexplode: "5,x",
+                formDataExplode: "5=x",
+                formDataUnexplode: "keys=5,x",
+                deepObjectExplode: "keys%5B5%5D=x"
+            )
+        )
+        try _test(
+            ["0": "zero"],
+            key: "keys",
+            .init(
+                formExplode: "0=zero",
+                formUnexplode: "keys=0,zero",
+                simpleExplode: "0=zero",
+                simpleUnexplode: "0,zero",
+                formDataExplode: "0=zero",
+                formDataUnexplode: "keys=0,zero",
+                deepObjectExplode: "keys%5B0%5D=zero"
+            )
+        )
+
+        // A dictionary of non-primitive values with a numeric-looking key.
+        try _test(
+            ["7": SimpleEnum.red],
+            key: "keys",
+            .init(
+                formExplode: "7=red",
+                formUnexplode: "keys=7,red",
+                simpleExplode: "7=red",
+                simpleUnexplode: "7,red",
+                formDataExplode: "7=red",
+                formDataUnexplode: "keys=7,red",
+                deepObjectExplode: "keys%5B7%5D=red"
+            )
+        )
+
+        // A free-form object with a numeric-looking key.
+        try _test(
+            OpenAPIObjectContainer(unvalidatedValue: ["5": "x"]),
+            key: "keys",
+            .init(
+                formExplode: "5=x",
+                formUnexplode: "keys=5,x",
+                simpleExplode: "5=x",
+                simpleUnexplode: "5,x",
+                formDataExplode: "5=x",
+                formDataUnexplode: "keys=5,x",
+                deepObjectExplode: "keys%5B5%5D=x"
+            )
+        )
+
         // An empty dictionary.
         try _test(
             [:] as [String: String],