diff --git a/src/ncp/spinel_encoder.hpp b/src/ncp/spinel_encoder.hpp
index 0fa96fab8..45e8e5cf0 100644
--- a/src/ncp/spinel_encoder.hpp
+++ b/src/ncp/spinel_encoder.hpp
@@ -59,7 +59,8 @@ public:
      * @param[in] aNcpBuffer   A reference to a `NcpFrameBuffer` where the frames are written.
      *
      */
-    SpinelEncoder(NcpFrameBuffer &aNcpBuffer): mNcpBuffer(aNcpBuffer), mNumOpenStructs(0) { }
+    SpinelEncoder(NcpFrameBuffer &aNcpBuffer):
+        mNcpBuffer(aNcpBuffer), mNumOpenStructs(0), mSavedNumOpenStructs(0), mSavedPosition() { }
 
     /**
      * This method begins a new frame to be added/written to the frame buffer.