diff --git a/Include/pgenheaders.h b/Include/pgenheaders.h
index 20ac2c7be99..051173cc5ee 100644
--- a/Include/pgenheaders.h
+++ b/Include/pgenheaders.h
@@ -25,8 +25,10 @@ extern "C" {
 
 #include "pydebug.h"
 
-DL_IMPORT(void) PySys_WriteStdout(const char *format, ...);
-DL_IMPORT(void) PySys_WriteStderr(const char *format, ...);
+DL_IMPORT(void) PySys_WriteStdout(const char *format, ...)
+			__attribute__((format(printf, 1, 2)));
+DL_IMPORT(void) PySys_WriteStderr(const char *format, ...)
+			__attribute__((format(printf, 1, 2)));
 
 #define addarc _Py_addarc
 #define addbit _Py_addbit
diff --git a/Include/pyerrors.h b/Include/pyerrors.h
index c3960b7e593..29ee1b6b000 100644
--- a/Include/pyerrors.h
+++ b/Include/pyerrors.h
@@ -77,7 +77,8 @@ extern DL_IMPORT(int) PyErr_BadArgument(void);
 extern DL_IMPORT(PyObject *) PyErr_NoMemory(void);
 extern DL_IMPORT(PyObject *) PyErr_SetFromErrno(PyObject *);
 extern DL_IMPORT(PyObject *) PyErr_SetFromErrnoWithFilename(PyObject *, char *);
-extern DL_IMPORT(PyObject *) PyErr_Format(PyObject *, const char *, ...);
+extern DL_IMPORT(PyObject *) PyErr_Format(PyObject *, const char *, ...)
+			__attribute__((format(printf, 2, 3)));
 #ifdef MS_WINDOWS
 extern DL_IMPORT(PyObject *) PyErr_SetFromWindowsErrWithFilename(int, const char *);
 extern DL_IMPORT(PyObject *) PyErr_SetFromWindowsErr(int);
@@ -126,8 +127,10 @@ extern DL_IMPORT(PyObject *) PyErr_ProgramText(char *, int);
 
 #ifndef HAVE_SNPRINTF
 #include <stdarg.h>
-extern DL_IMPORT(int) PyOS_snprintf(char *str, size_t size, const char  *format, ...);
-extern DL_IMPORT(int) PyOS_vsnprintf(char *str, size_t size, const char  *format, va_list va);
+extern DL_IMPORT(int) PyOS_snprintf(char *str, size_t size, const char  *format, ...)
+			__attribute__((format(printf, 3, 4)));
+extern DL_IMPORT(int) PyOS_vsnprintf(char *str, size_t size, const char  *format, va_list va)
+			__attribute__((format(printf, 3, 0)));
 #else
 # define PyOS_vsnprintf	vsnprintf
 # define PyOS_snprintf	snprintf
diff --git a/Include/stringobject.h b/Include/stringobject.h
index 052eacf85e3..a5d97fa891b 100644
--- a/Include/stringobject.h
+++ b/Include/stringobject.h
@@ -56,8 +56,10 @@ extern DL_IMPORT(PyTypeObject) PyString_Type;
 
 extern DL_IMPORT(PyObject *) PyString_FromStringAndSize(const char *, int);
 extern DL_IMPORT(PyObject *) PyString_FromString(const char *);
-extern DL_IMPORT(PyObject *) PyString_FromFormatV(const char*, va_list);
-extern DL_IMPORT(PyObject *) PyString_FromFormat(const char*, ...);
+extern DL_IMPORT(PyObject *) PyString_FromFormatV(const char*, va_list)
+				__attribute__((format(printf, 1, 0)));
+extern DL_IMPORT(PyObject *) PyString_FromFormat(const char*, ...)
+				__attribute__((format(printf, 1, 2)));
 extern DL_IMPORT(int) PyString_Size(PyObject *);
 extern DL_IMPORT(char *) PyString_AsString(PyObject *);
 extern DL_IMPORT(void) PyString_Concat(PyObject **, PyObject *);
diff --git a/Include/sysmodule.h b/Include/sysmodule.h
index 92f2207be3d..ca6b6d78982 100644
--- a/Include/sysmodule.h
+++ b/Include/sysmodule.h
@@ -13,8 +13,10 @@ DL_IMPORT(FILE *) PySys_GetFile(char *, FILE *);
 DL_IMPORT(void) PySys_SetArgv(int, char **);
 DL_IMPORT(void) PySys_SetPath(char *);
 
-DL_IMPORT(void) PySys_WriteStdout(const char *format, ...);
-DL_IMPORT(void) PySys_WriteStderr(const char *format, ...);
+DL_IMPORT(void) PySys_WriteStdout(const char *format, ...)
+			__attribute__((format(printf, 1, 2)));
+DL_IMPORT(void) PySys_WriteStderr(const char *format, ...)
+			__attribute__((format(printf, 1, 2)));
 
 extern DL_IMPORT(PyObject *) _PySys_TraceFunc, *_PySys_ProfileFunc;
 extern DL_IMPORT(int) _PySys_CheckInterval;