diff --git a/src/_avif.c b/src/_avif.c
index 4fd5de37267..5553f84e5be 100644
--- a/src/_avif.c
+++ b/src/_avif.c
@@ -1,7 +1,7 @@
 #define PY_SSIZE_T_CLEAN
 
 #include <Python.h>
-#include "avif/avif.h"
+#include <avif/avif.h>
 
 // Encoder type
 typedef struct {
diff --git a/src/_imaging.c b/src/_imaging.c
index 04b5da3f68c..dd256e9dc4f 100644
--- a/src/_imaging.c
+++ b/src/_imaging.c
@@ -72,21 +72,21 @@
  */
 
 #define PY_SSIZE_T_CLEAN
-#include "Python.h"
+#include <Python.h>
 
 #ifdef HAVE_LIBJPEG
-#include "jconfig.h"
+#include <jconfig.h>
 #ifdef LIBJPEG_TURBO_VERSION
 #define JCONFIG_INCLUDED
 #ifdef __CYGWIN__
 #define _BASETSD_H
 #endif
-#include "jpeglib.h"
+#include <jpeglib.h>
 #endif
 #endif
 
 #ifdef HAVE_LIBZ
-#include "zlib.h"
+#include <zlib.h>
 #endif
 
 #ifdef HAVE_LIBTIFF
diff --git a/src/_imagingcms.c b/src/_imagingcms.c
index 993b80ec5b0..b672abb2473 100644
--- a/src/_imagingcms.c
+++ b/src/_imagingcms.c
@@ -27,11 +27,11 @@ kevin@cazabon.com\n\
 "
 
 #define PY_SSIZE_T_CLEAN
-#include "Python.h"  // Include before wchar.h so _GNU_SOURCE is set
-#include "wchar.h"
-#include "datetime.h"
+#include <Python.h>  // Include before wchar.h so _GNU_SOURCE is set
+#include <wchar.h>
+#include <datetime.h>
 
-#include "lcms2.h"
+#include <lcms2.h>
 #include "libImaging/Imaging.h"
 
 #define PYCMSVERSION "1.0.0 pil"
diff --git a/src/_imagingft.c b/src/_imagingft.c
index 4b49eb04766..dd795ed2e66 100644
--- a/src/_imagingft.c
+++ b/src/_imagingft.c
@@ -19,7 +19,7 @@
  */
 
 #define PY_SSIZE_T_CLEAN
-#include "Python.h"
+#include <Python.h>
 #include "thirdparty/pythoncapi_compat.h"
 #include "libImaging/Imaging.h"
 
diff --git a/src/_imagingmath.c b/src/_imagingmath.c
index 1fe517f0431..66015ca32d7 100644
--- a/src/_imagingmath.c
+++ b/src/_imagingmath.c
@@ -13,12 +13,12 @@
  * See the README file for information on usage and redistribution.
  */
 
-#include "Python.h"
+#include <Python.h>
 
 #include "libImaging/Imaging.h"
 
-#include "math.h"
-#include "float.h"
+#include <math.h>
+#include <float.h>
 
 #define MAX_INT32 2147483647.0
 #define MIN_INT32 -2147483648.0
diff --git a/src/_imagingtk.c b/src/_imagingtk.c
index 7b9607cb5e2..9108ded03bd 100644
--- a/src/_imagingtk.c
+++ b/src/_imagingtk.c
@@ -12,7 +12,7 @@
  * See the README file for information on usage and redistribution.
  */
 
-#include "Python.h"
+#include <Python.h>
 #include "libImaging/Imaging.h"
 
 #include "Tk/_tkmini.h"
diff --git a/src/decode.c b/src/decode.c
index 5055ebb03fc..bdb8b0a2dbc 100644
--- a/src/decode.c
+++ b/src/decode.c
@@ -30,7 +30,7 @@
 /* FIXME: make these pluggable! */
 
 #define PY_SSIZE_T_CLEAN
-#include "Python.h"
+#include <Python.h>
 
 #include "libImaging/Imaging.h"
 
diff --git a/src/display.c b/src/display.c
index 4a2d9d9b256..a950cffc127 100644
--- a/src/display.c
+++ b/src/display.c
@@ -23,7 +23,7 @@
  */
 
 #define PY_SSIZE_T_CLEAN
-#include "Python.h"
+#include <Python.h>
 
 #include "libImaging/Imaging.h"
 
diff --git a/src/encode.c b/src/encode.c
index c0c956046a9..f4e752ea7ad 100644
--- a/src/encode.c
+++ b/src/encode.c
@@ -23,7 +23,7 @@
 /* FIXME: make these pluggable! */
 
 #define PY_SSIZE_T_CLEAN
-#include "Python.h"
+#include <Python.h>
 
 #include "thirdparty/pythoncapi_compat.h"
 #include "libImaging/Imaging.h"
diff --git a/src/libImaging/Fill.c b/src/libImaging/Fill.c
index 25344cf3a7e..ea61a0ff031 100644
--- a/src/libImaging/Fill.c
+++ b/src/libImaging/Fill.c
@@ -17,7 +17,7 @@
 
 #include "Imaging.h"
 
-#include "math.h"
+#include <math.h>
 
 Imaging
 ImagingFill(Imaging im, const void *colour) {
diff --git a/src/libImaging/ImPlatform.h b/src/libImaging/ImPlatform.h
index ec871d31132..a800d8278f9 100644
--- a/src/libImaging/ImPlatform.h
+++ b/src/libImaging/ImPlatform.h
@@ -8,7 +8,7 @@
  */
 
 #define PY_SSIZE_T_CLEAN
-#include "Python.h"
+#include <Python.h>
 
 /* Check that we have an ANSI compliant compiler */
 #ifndef HAVE_PROTOTYPES
diff --git a/src/libImaging/Jpeg.h b/src/libImaging/Jpeg.h
index e07904fc70c..5b795430c1a 100644
--- a/src/libImaging/Jpeg.h
+++ b/src/libImaging/Jpeg.h
@@ -8,7 +8,7 @@
  * Copyright (c) 1995-1996 by Fredrik Lundh
  */
 
-#include "jpeglib.h"
+#include <jpeglib.h>
 
 #include <setjmp.h>
 
diff --git a/src/libImaging/ZipCodecs.h b/src/libImaging/ZipCodecs.h
index 50218b6c69a..42f1a710150 100644
--- a/src/libImaging/ZipCodecs.h
+++ b/src/libImaging/ZipCodecs.h
@@ -7,7 +7,7 @@
  * Copyright (c) Fredrik Lundh 1996.
  */
 
-#include "zlib.h"
+#include <zlib.h>
 
 /* modes */
 #define ZIP_PNG 0            /* continuous, filtered image data */
diff --git a/src/libImaging/codec_fd.c b/src/libImaging/codec_fd.c
index c5614e6039b..2e792a85adf 100644
--- a/src/libImaging/codec_fd.c
+++ b/src/libImaging/codec_fd.c
@@ -1,4 +1,4 @@
-#include "Python.h"
+#include <Python.h>
 #include "Imaging.h"
 
 Py_ssize_t
diff --git a/src/map.c b/src/map.c
index 4c9bb2ae34c..23cf1df2ffe 100644
--- a/src/map.c
+++ b/src/map.c
@@ -18,7 +18,7 @@
  * FIXME: should move the memory mapping primitives into libImaging!
  */
 
-#include "Python.h"
+#include <Python.h>
 
 #include "libImaging/Imaging.h"
 
diff --git a/src/outline.c b/src/outline.c
index 32ab9109c15..2ca388ee52b 100644
--- a/src/outline.c
+++ b/src/outline.c
@@ -17,7 +17,7 @@
  * See the README file for information on usage and redistribution.
  */
 
-#include "Python.h"
+#include <Python.h>
 
 #include "libImaging/Imaging.h"
 
diff --git a/src/path.c b/src/path.c
index 4b1b16361d5..d390247b292 100644
--- a/src/path.c
+++ b/src/path.c
@@ -25,7 +25,7 @@
  * See the README file for information on usage and redistribution.
  */
 
-#include "Python.h"
+#include <Python.h>
 #include "thirdparty/pythoncapi_compat.h"
 #include "libImaging/Imaging.h"