diff --git a/src/SoftwareSerial.cpp b/src/SoftwareSerial.cpp
index 84d2f3f..b733a40 100644
--- a/src/SoftwareSerial.cpp
+++ b/src/SoftwareSerial.cpp
@@ -89,16 +89,14 @@ void SoftwareSerial::begin(uint32_t baud, SoftwareSerialConfig config,
     m_bitCycles = (ESP.getCpuFreqMHz() * 1000000UL + baud / 2) / baud;
     m_intTxEnabled = true;
     if (isValidRxGPIOpin(m_rxPin)) {
-        std::unique_ptr<circular_queue<uint8_t> > buffer(new circular_queue<uint8_t>((bufCapacity > 0) ? bufCapacity : 64));
-        m_buffer = move(buffer);
+        m_buffer.reset(new circular_queue<uint8_t>((bufCapacity > 0) ? bufCapacity : 64));
         if (m_parityMode)
         {
-            std::unique_ptr<circular_queue<uint8_t> > parityBuffer(new circular_queue<uint8_t>((bufCapacity > 0) ? (bufCapacity + 7) / 8 : 8));
-            m_parityBuffer = move(parityBuffer);
+            m_parityBuffer.reset(new circular_queue<uint8_t>((m_buffer->capacity() + 7) / 8));
             m_parityInPos = m_parityOutPos = 1;
         }
-        std::unique_ptr<circular_queue<uint32_t> > isrBuffer(new circular_queue<uint32_t>((isrBufCapacity > 0) ? isrBufCapacity : (sizeof(uint8_t) * 8 + 2) * bufCapacity));
-        m_isrBuffer = move(isrBuffer);
+        m_isrBuffer.reset(new circular_queue<uint32_t>((isrBufCapacity > 0) ?
+            isrBufCapacity : m_buffer->capacity() * (2 + m_dataBits + static_cast<bool>(m_parityMode))));
         if (m_buffer && (!m_parityMode || m_parityBuffer) && m_isrBuffer) {
             m_rxValid = true;
             pinMode(m_rxPin, INPUT_PULLUP);