diff --git a/ch09/exercise9_43.cpp b/ch09/exercise9_43.cpp
index 6d2e938..2405ea8 100644
--- a/ch09/exercise9_43.cpp
+++ b/ch09/exercise9_43.cpp
@@ -6,7 +6,7 @@ using namespace std;
 void replace(string& s, const string& oldVal, const string& newVal)
 {
 	auto curr = s.begin();
-	while (curr != s.end() - oldVal.size())
+	while (curr <= s.end() - oldVal.size())
 	{
 		if (oldVal == string(curr, curr + oldVal.size()))
 		{
@@ -28,4 +28,4 @@ int main()
 	replace(s, "thru", "through");
 
 	cout << s;
-}
\ No newline at end of file
+}