diff --git a/stepmania/src/crypto51/cryptlib.h b/stepmania/src/crypto51/cryptlib.h
index dd30f6432f..987ba97001 100644
--- a/stepmania/src/crypto51/cryptlib.h
+++ b/stepmania/src/crypto51/cryptlib.h
@@ -331,6 +331,7 @@ public:
 class SimpleKeyingInterface
 {
 public:
+	virtual ~SimpleKeyingInterface() { }
 	//! returns smallest valid key length in bytes */
 	virtual unsigned int MinKeyLength() const =0;
 	//! returns largest valid key length in bytes */
@@ -632,6 +633,7 @@ class WaitObjectContainer;
 class Waitable
 {
 public:
+	virtual ~Waitable() { }
 	//! maximum number of wait objects that this object can return
 	virtual unsigned int GetMaxWaitObjectCount() const =0;
 	//! put wait objects into container
diff --git a/stepmania/src/crypto51/nbtheory.h b/stepmania/src/crypto51/nbtheory.h
index 21a9e2d1db..52ae6e89f9 100644
--- a/stepmania/src/crypto51/nbtheory.h
+++ b/stepmania/src/crypto51/nbtheory.h
@@ -44,6 +44,7 @@ bool VerifyPrime(RandomNumberGenerator &rng, const Integer &p, unsigned int leve
 class PrimeSelector
 {
 public:
+	virtual ~PrimeSelector() {}
 	const PrimeSelector *GetSelectorPointer() const {return this;}
 	virtual bool IsAcceptable(const Integer &candidate) const =0;
 };
diff --git a/stepmania/src/crypto51/pubkey.h b/stepmania/src/crypto51/pubkey.h
index 5bb3cadbca..4c08bab004 100644
--- a/stepmania/src/crypto51/pubkey.h
+++ b/stepmania/src/crypto51/pubkey.h
@@ -109,6 +109,8 @@ public:
 template <class TFI, class MEI>
 class TF_Base
 {
+public:
+	virtual ~TF_Base() {}
 protected:
 	virtual const TrapdoorFunctionBounds & GetTrapdoorFunctionBounds() const =0;
 
@@ -314,6 +316,7 @@ template <class KEYS>
 class PublicKeyCopier
 {
 public:
+	virtual ~PublicKeyCopier() {}
 	virtual void CopyKeyInto(typename KEYS::PublicKey &key) const =0;
 };
 
@@ -322,6 +325,7 @@ template <class KEYS>
 class PrivateKeyCopier
 {
 public:
+	virtual ~PrivateKeyCopier() {}
 	virtual void CopyKeyInto(typename KEYS::PublicKey &key) const =0;
 	virtual void CopyKeyInto(typename KEYS::PrivateKey &key) const =0;
 };