diff --git a/config.h b/config.h
index ab00dc7a..0d99df57 100644
--- a/config.h
+++ b/config.h
@@ -546,7 +546,7 @@ NAMESPACE_END
 
 // How to declare class constants
 // Use enum for OS X 10.5 ld, http://github.com/weidai11/cryptopp/issues/255
-#if (defined(_MSC_VER) && _MSC_VER <= 1300) || defined(__INTEL_COMPILER) || defined(__BORLANDC__) || (defined(__APPLE__) && (__GNUC__ == 4) && (__GNUC_MINOR__ <= 2))
+#if (defined(_MSC_VER) && _MSC_VER <= 1300) || defined(__INTEL_COMPILER) || defined(__BORLANDC__)
 #	define CRYPTOPP_CONSTANT(x) enum {x};
 #else
 #	define CRYPTOPP_CONSTANT(x) static const int x;
diff --git a/config.recommend b/config.recommend
index 61fcb1df..966a6da8 100644
--- a/config.recommend
+++ b/config.recommend
@@ -546,7 +546,7 @@ NAMESPACE_END
 
 // How to declare class constants
 // Use enum for OS X 10.5 ld, http://github.com/weidai11/cryptopp/issues/255
-#if (defined(_MSC_VER) && _MSC_VER <= 1300) || defined(__INTEL_COMPILER) || defined(__BORLANDC__) || (defined(__APPLE__) && (__GNUC__ == 4) && (__GNUC_MINOR__ <= 2))
+#if (defined(_MSC_VER) && _MSC_VER <= 1300) || defined(__INTEL_COMPILER) || defined(__BORLANDC__)
 #	define CRYPTOPP_CONSTANT(x) enum {x};
 #else
 #	define CRYPTOPP_CONSTANT(x) static const int x;
diff --git a/seckey.h b/seckey.h
index 31286ce6..bbf1ea7a 100644
--- a/seckey.h
+++ b/seckey.h
@@ -71,11 +71,20 @@ public:
 	//! \param keylength the size of the key, in bytes
 	//! \details keylength is unused in the default implementation.
 	CRYPTOPP_CONSTEXPR static unsigned int StaticGetDefaultRounds(size_t keylength)
-		{return CRYPTOPP_UNUSED(keylength), DEFAULT_ROUNDS;}
+	{
+		// Comma operator breaks Debug builds with GCC 4.0 - 4.6.
+		// Also see http://github.com/weidai11/cryptopp/issues/255
+#if defined(CRYPTOPP_CXX11_CONSTEXPR)
+		return CRYPTOPP_UNUSED(keylength), static_cast<unsigned int>(DEFAULT_ROUNDS);
+#else
+		CRYPTOPP_UNUSED(keylength);
+		return static_cast<unsigned int>(DEFAULT_ROUNDS);
+#endif
+	}
 
 protected:
 	//! \brief Validates the number of rounds for an algorithm.
-	//! \param rounds the canddiate number of rounds
+	//! \param rounds the candidate number of rounds
 	//! \param alg an Algorithm object used if the number of rounds are invalid
 	//! \throws InvalidRounds if the number of rounds are invalid
 	//! \details ThrowIfInvalidRounds() validates the number of rounds and throws if invalid.
@@ -94,7 +103,7 @@ protected:
 	}
 
 	//! \brief Validates the number of rounds for an algorithm
-	//! \param param the canddiate number of rounds
+	//! \param param the candidate number of rounds
 	//! \param alg an Algorithm object used if the number of rounds are invalid
 	//! \returns the number of rounds for the algorithm
 	//! \throws InvalidRounds if the number of rounds are invalid
@@ -143,7 +152,16 @@ public:
 	//! \details The default implementation returns KEYLENGTH. keylength is unused
 	//!   in the default implementation.
 	CRYPTOPP_CONSTEXPR static size_t CRYPTOPP_API StaticGetValidKeyLength(size_t keylength)
-		{return CRYPTOPP_UNUSED(keylength), KEYLENGTH;}
+	{
+		// Comma operator breaks Debug builds with GCC 4.0 - 4.6.
+		// Also see http://github.com/weidai11/cryptopp/issues/255
+#if defined(CRYPTOPP_CXX11_CONSTEXPR)
+		return CRYPTOPP_UNUSED(keylength), static_cast<size_t>(KEYLENGTH);
+#else
+		CRYPTOPP_UNUSED(keylength);
+		return static_cast<size_t>(KEYLENGTH);
+#endif
+	}
 };
 
 //! \class VariableKeyLength
diff --git a/validat1.cpp b/validat1.cpp
index afda0d94..66285929 100644
--- a/validat1.cpp
+++ b/validat1.cpp
@@ -2436,6 +2436,7 @@ bool ValidateRC5()
 	bool pass1 = true, pass2 = true;
 
 	RC5Encryption enc;  // 0 to 2040-bits (255-bytes)
+	pass1 = RC5Encryption::DEFAULT_KEYLENGTH ==  16 && pass1;
 	pass1 = enc.StaticGetValidKeyLength(0) == 0 && pass1;
 	pass1 = enc.StaticGetValidKeyLength(254) == 254 && pass1;
 	pass1 = enc.StaticGetValidKeyLength(255) == 255 && pass1;
@@ -2444,6 +2445,7 @@ bool ValidateRC5()
 	pass1 = enc.StaticGetValidKeyLength(SIZE_MAX) == enc.MaxKeyLength() && pass1;
 
 	RC5Decryption dec;
+	pass2 = RC5Decryption::DEFAULT_KEYLENGTH ==  16 && pass2;
 	pass2 = dec.StaticGetValidKeyLength(0) == 0 && pass2;
 	pass2 = dec.StaticGetValidKeyLength(254) == 254 && pass2;
 	pass2 = dec.StaticGetValidKeyLength(255) == 255 && pass2;
@@ -2684,11 +2686,13 @@ bool ValidateThreeWay()
 	bool pass1 = true, pass2 = true;
 
 	ThreeWayEncryption enc;  // 96-bit only
+	pass1 = ThreeWayEncryption::KEYLENGTH ==  12 && pass1;
 	pass1 = enc.StaticGetValidKeyLength(8) == 12 && pass1;
 	pass1 = enc.StaticGetValidKeyLength(12) == 12 && pass1;
 	pass1 = enc.StaticGetValidKeyLength(16) == 12 && pass1;
 
 	ThreeWayDecryption dec;  // 96-bit only
+	pass2 = ThreeWayEncryption::KEYLENGTH ==  12 && pass2;
 	pass2 = dec.StaticGetValidKeyLength(8) == 12 && pass2;
 	pass2 = dec.StaticGetValidKeyLength(12) == 12 && pass2;
 	pass2 = dec.StaticGetValidKeyLength(16) == 12 && pass2;