diff --git a/core/string/ustring.cpp b/core/string/ustring.cpp
index 7e1785e8c..f8de2eb57 100644
--- a/core/string/ustring.cpp
+++ b/core/string/ustring.cpp
@@ -926,7 +926,7 @@ String String::substr(int p_from, int p_chars) const {
 String String::substr_index(const int start_index, const int end_index) const {
 	int s = length();
 
-	if (start_index < 0 || start_index >= s || end_index < 0 || start_index >= s) {
+	if (start_index < 0 || start_index >= s || end_index < 0) {
 		return "";
 	}
 
@@ -934,6 +934,10 @@ String String::substr_index(const int start_index, const int end_index) const {
 		return "";
 	}
 
+	if (end_index >= s) {
+		return substr(start_index, (s - 1) - start_index);
+	}
+
 	return substr(start_index, end_index - start_index);
 }