diff --git a/src/engine/demo.h b/src/engine/demo.h
index bf3b2e050..9fa5cc1cf 100644
--- a/src/engine/demo.h
+++ b/src/engine/demo.h
@@ -94,7 +94,7 @@ public:
 		TICK_NEXT, // go to the next tick
 	};
 
-	~IDemoPlayer() {}
+	virtual ~IDemoPlayer() {}
 	virtual void SetSpeed(float Speed) = 0;
 	virtual void SetSpeedIndex(int SpeedIndex) = 0;
 	virtual void AdjustSpeedIndex(int Offset) = 0;
@@ -115,7 +115,7 @@ class IDemoRecorder : public IInterface
 {
 	MACRO_INTERFACE("demorecorder", 0)
 public:
-	~IDemoRecorder() {}
+	virtual ~IDemoRecorder() {}
 	virtual bool IsRecording() const = 0;
 	virtual int Stop() = 0;
 	virtual int Length() const = 0;
diff --git a/src/engine/shared/demo.cpp b/src/engine/shared/demo.cpp
index 03441ddfd..3cf554540 100644
--- a/src/engine/shared/demo.cpp
+++ b/src/engine/shared/demo.cpp
@@ -43,9 +43,16 @@ CDemoRecorder::CDemoRecorder(class CSnapshotDelta *pSnapshotDelta, bool NoMapDat
 	m_NoMapData = NoMapData;
 }
 
+CDemoRecorder::~CDemoRecorder()
+{
+	dbg_assert(m_File == 0, "Demo recorder was not stopped");
+}
+
 // Record
 int CDemoRecorder::Start(class IStorage *pStorage, class IConsole *pConsole, const char *pFilename, const char *pNetVersion, const char *pMap, SHA256_DIGEST *pSha256, unsigned Crc, const char *pType, unsigned MapSize, unsigned char *pMapData, IOHANDLE MapFile, DEMOFUNC_FILTER pfnFilter, void *pUser)
 {
+	dbg_assert(m_File == 0, "Demo recorder already recording");
+
 	m_pfnFilter = pfnFilter;
 	m_pUser = pUser;
 
@@ -64,12 +71,6 @@ int CDemoRecorder::Start(class IStorage *pStorage, class IConsole *pConsole, con
 		return -1;
 	}
 
-	if(m_File)
-	{
-		io_close(DemoFile);
-		return -1;
-	}
-
 	bool CloseMapFile = false;
 
 	if(MapFile)
@@ -407,6 +408,11 @@ CDemoPlayer::CDemoPlayer(class CSnapshotDelta *pSnapshotDelta)
 	Construct(pSnapshotDelta);
 }
 
+CDemoPlayer::~CDemoPlayer()
+{
+	dbg_assert(m_File == 0, "Demo player not stopped");
+}
+
 void CDemoPlayer::Construct(class CSnapshotDelta *pSnapshotDelta)
 {
 	m_File = 0;
@@ -718,6 +724,8 @@ void CDemoPlayer::Unpause()
 
 int CDemoPlayer::Load(class IStorage *pStorage, class IConsole *pConsole, const char *pFilename, int StorageType)
 {
+	dbg_assert(m_File == 0, "Demo player already playing");
+
 	m_pConsole = pConsole;
 	m_File = pStorage->OpenFile(pFilename, IOFLAG_READ, StorageType);
 	if(!m_File)
diff --git a/src/engine/shared/demo.h b/src/engine/shared/demo.h
index 22c2373df..17f13874d 100644
--- a/src/engine/shared/demo.h
+++ b/src/engine/shared/demo.h
@@ -37,6 +37,7 @@ class CDemoRecorder : public IDemoRecorder
 public:
 	CDemoRecorder(class CSnapshotDelta *pSnapshotDelta, bool NoMapData = false);
 	CDemoRecorder() {}
+	~CDemoRecorder() override;
 
 	int Start(class IStorage *pStorage, class IConsole *pConsole, const char *pFilename, const char *pNetversion, const char *pMap, SHA256_DIGEST *pSha256, unsigned MapCrc, const char *pType, unsigned MapSize, unsigned char *pMapData, IOHANDLE MapFile = nullptr, DEMOFUNC_FILTER pfnFilter = nullptr, void *pUser = nullptr);
 	int Stop() override;
@@ -126,6 +127,7 @@ private:
 public:
 	CDemoPlayer(class CSnapshotDelta *pSnapshotDelta);
 	CDemoPlayer(class CSnapshotDelta *pSnapshotDelta, TUpdateIntraTimesFunc &&UpdateIntraTimesFunc);
+	~CDemoPlayer() override;
 
 	void Construct(class CSnapshotDelta *pSnapshotDelta);