diff --git a/src/builtins/string.cpp b/src/builtins/string.cpp
index 9c90cc888..e1d7a91a8 100644
--- a/src/builtins/string.cpp
+++ b/src/builtins/string.cpp
@@ -6,6 +6,7 @@
 #include <climits>
 #include <cstdarg>
 #include <cstddef>
+#include <cstdint>
 #include <cwchar>
 #include <cwctype>
 #include <map>
diff --git a/src/fallback.cpp b/src/fallback.cpp
index ee52a6a8a..a9ad1e1fc 100644
--- a/src/fallback.cpp
+++ b/src/fallback.cpp
@@ -9,10 +9,10 @@
 #include <errno.h>   // IWYU pragma: keep
 #include <fcntl.h>   // IWYU pragma: keep
 #include <limits.h>  // IWYU pragma: keep
-#include <unistd.h>
 #include <wctype.h>
 
 #include <cwchar>
+#include <cstdlib>
 #if HAVE_GETTEXT
 #include <libintl.h>
 #endif
diff --git a/src/fallback.h b/src/fallback.h
index 6cfdb2041..79ed82812 100644
--- a/src/fallback.h
+++ b/src/fallback.h
@@ -3,7 +3,6 @@
 
 #include "config.h"
 
-#include <stdint.h>
 // The following include must be kept despite what IWYU says. That's because of the interaction
 // between the weak linking of `wcscasecmp` via `#define`s below and the declarations
 // in <wchar.h>. At least on OS X if we don't do this we get compilation errors do to the macro