diff --git a/src/runtime/runtime-strings.cc b/src/runtime/runtime-strings.cc
index 6786fa9..0f19bf3 100644
--- a/src/runtime/runtime-strings.cc
+++ b/src/runtime/runtime-strings.cc
@@ -5,10 +5,7 @@
 #include "src/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
-#include "src/conversions-inl.h"
-#include "src/isolate-inl.h"
 #include "src/regexp/jsregexp-inl.h"
-#include "src/regexp/jsregexp.h"
 #include "src/string-builder.h"
 #include "src/string-search.h"
 
@@ -1080,7 +1077,7 @@
 
 RUNTIME_FUNCTION(Runtime_StringToLowerCase) {
   HandleScope scope(isolate);
-  DCHECK(args.length() == 1);
+  DCHECK_EQ(args.length(), 1);
   CONVERT_ARG_HANDLE_CHECKED(String, s, 0);
   return ConvertCase(s, isolate, isolate->runtime_state()->to_lower_mapping());
 }
@@ -1088,7 +1085,7 @@
 
 RUNTIME_FUNCTION(Runtime_StringToUpperCase) {
   HandleScope scope(isolate);
-  DCHECK(args.length() == 1);
+  DCHECK_EQ(args.length(), 1);
   CONVERT_ARG_HANDLE_CHECKED(String, s, 0);
   return ConvertCase(s, isolate, isolate->runtime_state()->to_upper_mapping());
 }
@@ -1154,6 +1151,7 @@
   return *result;
 }
 
+
 RUNTIME_FUNCTION(Runtime_StringLessThan) {
   HandleScope handle_scope(isolate);
   DCHECK_EQ(2, args.length());
@@ -1273,6 +1271,13 @@
   return __RT_impl_Runtime_StringCharFromCode(Arguments(1, &code), isolate);
 }
 
+RUNTIME_FUNCTION(Runtime_ExternalStringGetChar) {
+  SealHandleScope shs(isolate);
+  DCHECK_EQ(2, args.length());
+  CONVERT_ARG_CHECKED(ExternalString, string, 0);
+  CONVERT_INT32_ARG_CHECKED(index, 1);
+  return Smi::FromInt(string->Get(index));
+}
 
 RUNTIME_FUNCTION(Runtime_OneByteSeqStringGetChar) {
   SealHandleScope shs(isolate);