diff --git a/modules/seq/base/src/alignment_handle.cc b/modules/seq/base/src/alignment_handle.cc
index cf19f5a13fb6528469707f029d13150424af76f4..62514274c110d8d6389122f848e76feef3042be8 100644
--- a/modules/seq/base/src/alignment_handle.cc
+++ b/modules/seq/base/src/alignment_handle.cc
@@ -203,8 +203,8 @@ void AlignmentHandle::ShiftRegion(int start, int end, int amount,
 AlignedRegion AlignmentHandle::MakeRegion(int start, int n, int master) const
 {
   this->CheckValidity();
-  if(start<0 || n < 0 || start >= n || start + n > this->GetLength()){
-    throw std::out_of_range("Region not valid");
+  if((start<0 )||( n < 0 )|| ((start + n) > this->GetLength())){
+    throw std::out_of_range("invalid region");
   }
   return AlignedRegion(*this, start, start+n, master);
 }
diff --git a/modules/seq/base/src/impl/sequence_impl.cc b/modules/seq/base/src/impl/sequence_impl.cc
index 941d2c04230c9bbd2a4885e09cf4331d8fc270f1..c90e71c8982e53d11d5c8b176211c144060dd001 100644
--- a/modules/seq/base/src/impl/sequence_impl.cc
+++ b/modules/seq/base/src/impl/sequence_impl.cc
@@ -170,7 +170,7 @@ int SequenceImpl::GetLength() const {
 
 char SequenceImpl::GetOneLetterCode(int position) const
 {
-  if (position<0 || position>=static_cast<int>(seq_string_.length()))
+  if (position<0 || position>static_cast<int>(seq_string_.length()))
     throw Error("Position is not covered in sequence");
   return seq_string_[position];
 }
@@ -281,7 +281,7 @@ void SequenceImpl::Replace(const String& str,int start, int end)
 void SequenceImpl::ShiftRegion(int start, int end, int amount)
 {
   if(start > end || start + amount <= 0 || end + amount > this->GetLength()){
-    throw std::out_of_range("Region not valid");
+    throw std::out_of_range("ShiftRegion: invalid region");
   }
   String str1=seq_string_.substr(start, end-start);
   if (amount<0) {