diff --git a/src/common/StatusArg.cpp b/src/common/StatusArg.cpp
index 4ec888be9e..5a1c7693d2 100644
--- a/src/common/StatusArg.cpp
+++ b/src/common/StatusArg.cpp
@@ -52,6 +52,8 @@ Base::Base(ISC_STATUS k, ISC_STATUS c) :
 
 StatusVector::ImplStatusVector::ImplStatusVector(const ISC_STATUS* s) throw() : Base::ImplBase(0, 0)
 {
+	fb_assert(s);
+
 	clear();
 	// special case - empty initialized status vector, no warnings
 	if (s[0] != isc_arg_gds || s[1] != 0 || s[2] != 0)
@@ -113,6 +115,11 @@ bool StatusVector::ImplStatusVector::appendWarnings(const ImplBase* const v) thr
 
 bool StatusVector::ImplStatusVector::append(const ISC_STATUS* const from, const int count) throw()
 {
+	// CVC: I didn't expect count to be zero but it's, in some calls
+	fb_assert(count >= 0 && count <= ISC_STATUS_LENGTH);
+	if (!count)
+		return true; // not sure it's the best option here
+
 	unsigned int copied = 0;
 
 	for (int i = 0; i < count; )
@@ -175,8 +182,7 @@ void StatusVector::raise() const
 	{
 		status_exception::raise(*this);
 	}
-	status_exception::raise(Gds(isc_random) <<
-		Str("Attempt to raise empty exception"));
+	status_exception::raise(Gds(isc_random) << Str("Attempt to raise empty exception"));
 }
 
 ISC_STATUS StatusVector::ImplStatusVector::copyTo(ISC_STATUS* dest) const throw()
@@ -185,7 +191,8 @@ ISC_STATUS StatusVector::ImplStatusVector::copyTo(ISC_STATUS* dest) const throw(
 	{
 		memcpy(dest, value(), (length() + 1u) * sizeof(ISC_STATUS));
 	}
-	else {
+	else
+	{
 		dest[0] = isc_arg_gds;
 		dest[1] = FB_SUCCESS;
 		dest[2] = isc_arg_end;
diff --git a/src/common/classes/ClumpletReader.cpp b/src/common/classes/ClumpletReader.cpp
index 23cd73595f..f7a1308f94 100644
--- a/src/common/classes/ClumpletReader.cpp
+++ b/src/common/classes/ClumpletReader.cpp
@@ -545,6 +545,8 @@ const UCHAR* ClumpletReader::getBytes() const
 
 SINT64 ClumpletReader::fromVaxInteger(const UCHAR* ptr, size_t length)
 {
+	// We can't handle numbers bigger than int64. Some cases use length == 0.
+	fb_assert(ptr && length >= 0 && length < 9); 
 	// This code is taken from gds__vax_integer
 	SINT64 value = 0;
 	int shift = 0;
diff --git a/src/common/classes/ClumpletWriter.cpp b/src/common/classes/ClumpletWriter.cpp
index 0431cbb400..407a870b4b 100644
--- a/src/common/classes/ClumpletWriter.cpp
+++ b/src/common/classes/ClumpletWriter.cpp
@@ -134,6 +134,7 @@ void ClumpletWriter::size_overflow()
 
 void ClumpletWriter::toVaxInteger(UCHAR* ptr, size_t length, const SINT64 value)
 {
+	fb_assert(ptr && length > 0 && length < 9); // We can't handle numbers bigger than int64.
 	int shift = 0;
 	while (length--)
 	{