diff --git a/modules/openapi-generator/src/main/resources/swift5/Extensions.mustache b/modules/openapi-generator/src/main/resources/swift5/Extensions.mustache
index 6d59f14e753..92d0d1f95af 100644
--- a/modules/openapi-generator/src/main/resources/swift5/Extensions.mustache
+++ b/modules/openapi-generator/src/main/resources/swift5/Extensions.mustache
@@ -155,9 +155,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     {{#nonPublicApi}}internal{{/nonPublicApi}}{{^nonPublicApi}}public{{/nonPublicApi}} mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     {{#nonPublicApi}}internal{{/nonPublicApi}}{{^nonPublicApi}}public{{/nonPublicApi}} mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
index ac04dba5fbb..286c5001ff8 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
@@ -153,9 +153,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     public mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     public mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/anycodableLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift b/samples/client/petstore/swift5/anycodableLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
index ac04dba5fbb..286c5001ff8 100644
--- a/samples/client/petstore/swift5/anycodableLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
+++ b/samples/client/petstore/swift5/anycodableLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
@@ -153,9 +153,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     public mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     public mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/asyncAwaitLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift b/samples/client/petstore/swift5/asyncAwaitLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
index ac04dba5fbb..286c5001ff8 100644
--- a/samples/client/petstore/swift5/asyncAwaitLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
+++ b/samples/client/petstore/swift5/asyncAwaitLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
@@ -153,9 +153,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     public mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     public mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
index ac04dba5fbb..286c5001ff8 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
@@ -153,9 +153,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     public mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     public mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Extensions.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Extensions.swift
index ac04dba5fbb..286c5001ff8 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Extensions.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Extensions.swift
@@ -153,9 +153,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     public mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     public mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Extensions.swift b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Extensions.swift
index ac04dba5fbb..286c5001ff8 100644
--- a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Extensions.swift
+++ b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Extensions.swift
@@ -153,9 +153,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     public mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     public mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/frozenEnums/PetstoreClient/Classes/OpenAPIs/Extensions.swift b/samples/client/petstore/swift5/frozenEnums/PetstoreClient/Classes/OpenAPIs/Extensions.swift
index ac04dba5fbb..286c5001ff8 100644
--- a/samples/client/petstore/swift5/frozenEnums/PetstoreClient/Classes/OpenAPIs/Extensions.swift
+++ b/samples/client/petstore/swift5/frozenEnums/PetstoreClient/Classes/OpenAPIs/Extensions.swift
@@ -153,9 +153,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     public mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     public mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Extensions.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Extensions.swift
index 49859f31415..5ffd8f3a2fb 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Extensions.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Extensions.swift
@@ -153,9 +153,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     internal mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     internal mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Extensions.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Extensions.swift
index ac04dba5fbb..286c5001ff8 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Extensions.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Extensions.swift
@@ -153,9 +153,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     public mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     public mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/oneOf/PetstoreClient/Classes/OpenAPIs/Extensions.swift b/samples/client/petstore/swift5/oneOf/PetstoreClient/Classes/OpenAPIs/Extensions.swift
index ac04dba5fbb..286c5001ff8 100644
--- a/samples/client/petstore/swift5/oneOf/PetstoreClient/Classes/OpenAPIs/Extensions.swift
+++ b/samples/client/petstore/swift5/oneOf/PetstoreClient/Classes/OpenAPIs/Extensions.swift
@@ -153,9 +153,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     public mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     public mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
index 807343fdb56..c90549a4965 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
@@ -154,9 +154,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     public mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     public mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Extensions.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Extensions.swift
index ac04dba5fbb..286c5001ff8 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Extensions.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Extensions.swift
@@ -153,9 +153,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     public mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     public mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
index ac04dba5fbb..286c5001ff8 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Extensions.swift
@@ -153,9 +153,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     public mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     public mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/Sources/PetstoreClient/Extensions.swift b/samples/client/petstore/swift5/urlsessionLibrary/Sources/PetstoreClient/Extensions.swift
index ac04dba5fbb..286c5001ff8 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/Sources/PetstoreClient/Extensions.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/Sources/PetstoreClient/Extensions.swift
@@ -153,9 +153,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     public mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     public mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/validation/PetstoreClient/Classes/OpenAPIs/Extensions.swift b/samples/client/petstore/swift5/validation/PetstoreClient/Classes/OpenAPIs/Extensions.swift
index ac04dba5fbb..286c5001ff8 100644
--- a/samples/client/petstore/swift5/validation/PetstoreClient/Classes/OpenAPIs/Extensions.swift
+++ b/samples/client/petstore/swift5/validation/PetstoreClient/Classes/OpenAPIs/Extensions.swift
@@ -153,9 +153,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     public mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     public mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/vaporLibrary/Sources/PetstoreClient/Extensions.swift b/samples/client/petstore/swift5/vaporLibrary/Sources/PetstoreClient/Extensions.swift
index f926a897a94..d846f3e2b36 100644
--- a/samples/client/petstore/swift5/vaporLibrary/Sources/PetstoreClient/Extensions.swift
+++ b/samples/client/petstore/swift5/vaporLibrary/Sources/PetstoreClient/Extensions.swift
@@ -59,9 +59,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     public mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     public mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {
diff --git a/samples/client/petstore/swift5/x-swift-hashable/PetstoreClient/Classes/OpenAPIs/Extensions.swift b/samples/client/petstore/swift5/x-swift-hashable/PetstoreClient/Classes/OpenAPIs/Extensions.swift
index ac04dba5fbb..286c5001ff8 100644
--- a/samples/client/petstore/swift5/x-swift-hashable/PetstoreClient/Classes/OpenAPIs/Extensions.swift
+++ b/samples/client/petstore/swift5/x-swift-hashable/PetstoreClient/Classes/OpenAPIs/Extensions.swift
@@ -153,9 +153,12 @@ extension KeyedEncodingContainerProtocol {
     }
 
     public mutating func encode(_ value: Decimal, forKey key: Self.Key) throws {
-        var mutableValue = value
-        let stringValue = NSDecimalString(&mutableValue, Locale(identifier: "en_US"))
-        try encode(stringValue, forKey: key)
+        let decimalNumber = NSDecimalNumber(decimal: value)
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.locale = Locale(identifier: "en_US")
+        let formattedString = numberFormatter.string(from: decimalNumber) ?? "\(value)"
+        try encode(formattedString, forKey: key)
     }
 
     public mutating func encodeIfPresent(_ value: Decimal?, forKey key: Self.Key) throws {