diff --git a/NearbyShare/Connection/InboundNearbyConnection.swift b/NearbyShare/Connection/InboundNearbyConnection.swift
index c7434fd..e22d61b 100644
--- a/NearbyShare/Connection/InboundNearbyConnection.swift
+++ b/NearbyShare/Connection/InboundNearbyConnection.swift
@@ -127,7 +127,21 @@ class InboundNearbyConnection: NearbyConnection {
         case .sentPairedKeyResult:
             try processPairedKeyResultFrame(frame)
         case .receivedPairedKeyResult:
-            try processIntroductionFrame(frame)
+            if frame.hasV1, frame.v1.hasIntroduction {
+                try processIntroductionFrame(frame)
+                return
+            }
+            if frame.hasV1, frame.v1.hasType {
+                if frame.v1.type == .pairedKeyResult || frame.v1.type == .pairedKeyEncryption || frame.v1.type == .progressUpdate {
+                    log("[InboundNearbyConnection \(self.id)] Ignoring duplicate/intermediate transfer setup frame \(frame.v1.type) while waiting for introduction.")
+                    return
+                }
+                if frame.v1.type == .response, case .accept = frame.v1.connectionResponse.status {
+                    log("[InboundNearbyConnection \(self.id)] Ignoring accept response while waiting for introduction.")
+                    return
+                }
+            }
+            throw NearbyError.requiredFieldMissing("shareNearbyFrame.v1.introduction")
         default:
             if frame.hasV1, frame.v1.hasType, frame.v1.type == .progressUpdate {
                 // ignore progress updates
diff --git a/NearbyShare/Connection/NearbyConnection.swift b/NearbyShare/Connection/NearbyConnection.swift
index 97fff66..b04d26d 100644
--- a/NearbyShare/Connection/NearbyConnection.swift
+++ b/NearbyShare/Connection/NearbyConnection.swift
@@ -206,7 +206,7 @@ class NearbyConnection {
     
     
     private func receiveFrameAsync(length: UInt32) {
-        connection.receive(minimumIncompleteLength: Int(length), maximumLength: Int(length)) { [self] content, _, isComplete, _ in
+        connection.receive(minimumIncompleteLength: Int(length), maximumLength: Int(length)) { [self] content, _, isComplete, error in
             if self.connectionClosed {
                 log("[NearbyConnection \(self.id)] Received FIN from peer, connection closed.")
                 connection.cancel()
@@ -237,11 +237,23 @@ class NearbyConnection {
                 
                 return
             }
+            if let error = error {
+                log("[NearbyConnection \(self.id)] Error during receiveFrameAsync(length:): \(error)")
+                self.lastError = error
+                self.protocolError()
+                return
+            }
             guard let content = content else {
                 log("[NearbyConnection \(self.id)] Received nil content during receiveFrameAsync(length:). IsComplete: \(isComplete)")
                 self.protocolError()
                 return
             }
+            guard content.count == Int(length) else {
+                log("[NearbyConnection \(self.id)] Dropping partial frame body. Expected \(length) bytes, got \(content.count)")
+                self.lastError = NearbyError.protocolError("Unexpected frame body length")
+                self.protocolError()
+                return
+            }
             
             self.startAndResetHeartbeatTimer()
             self.processReceivedFrame(frameData: content)