diff --git a/SDKs/darwin/usr/include/stdlib.h b/SDKs/darwin/usr/include/stdlib.h
index cf65df4..c18c2e4 100644
--- a/SDKs/darwin/usr/include/stdlib.h
+++ b/SDKs/darwin/usr/include/stdlib.h
@@ -22,6 +22,7 @@
 typedef __SIZE_TYPE__ size_t;
 
 void abort(void) __attribute__((__noreturn__));
+int atoi(const char *);
 void free(void *);
 char *getenv(const char *);
 void *malloc(size_t);
diff --git a/SDKs/linux/usr/include/stdlib.h b/SDKs/linux/usr/include/stdlib.h
index b3755df..2fe745a 100644
--- a/SDKs/linux/usr/include/stdlib.h
+++ b/SDKs/linux/usr/include/stdlib.h
@@ -22,6 +22,7 @@
 typedef __SIZE_TYPE__ size_t;
 
 void abort(void) __attribute__((__nothrow__)) __attribute__((__noreturn__));
+void atoi(const char *) __attribute__((__nothrow__));
 void free(void *) __attribute__((__nothrow__));
 char *getenv(const char *) __attribute__((__nothrow__))
   __attribute__((__nonnull__(1)));