diff --git a/core/string/ustring.cpp b/core/string/ustring.cpp
index 05c80296c29..cf0040353dd 100644
--- a/core/string/ustring.cpp
+++ b/core/string/ustring.cpp
@@ -3772,9 +3772,9 @@ String String::uri_encode() const {
 		} else {
 			char h_Val[3];
 #if defined(__GNUC__) || defined(_MSC_VER)
-			snprintf(h_Val, 3, "%hhX", ord);
+			snprintf(h_Val, 3, "%02hhX", ord);
 #else
-			sprintf(h_Val, "%hhX", ord);
+			sprintf(h_Val, "%02hhX", ord);
 #endif
 			res += "%";
 			res += h_Val;