diff --git a/LibC/stdlib.cpp b/LibC/stdlib.cpp
index 63583ab77b..7f323c204d 100644
--- a/LibC/stdlib.cpp
+++ b/LibC/stdlib.cpp
@@ -103,11 +103,17 @@ int atoi(const char* str)
             continue;
         }
         if (str[i] < '0' || str[i] > '9')
-            return 0;
+            return value;
         value = value * 10;
         value += str[i] - '0';
     }
     return isNegative ? -value : value;
 }
 
+long atol(const char* str)
+{
+    static_assert(sizeof(int) == sizeof(long));
+    return atoi(str);
+}
+
 }
diff --git a/LibC/stdlib.h b/LibC/stdlib.h
index 0cd6a8e2c8..b8d4174dbd 100644
--- a/LibC/stdlib.h
+++ b/LibC/stdlib.h
@@ -11,6 +11,7 @@ void* calloc(size_t nmemb, size_t);
 void* realloc(void *ptr, size_t);
 char* getenv(const char* name);
 int atoi(const char*);
+long atol(const char*);
 
 void exit(int status) __NORETURN;
 void abort() __NORETURN;