diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 352a8644b1..838029bf23 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2018-08-07  Tom Tromey  <tom@tromey.com>
+
+	* Makefile.in (CPPFLAGS): New variable.
+	(INTERNAL_CPPFLAGS): Use it.
+
 2018-08-07  Simon Marchi  <simon.marchi@ericsson.com>
 
 	* NEWS: Mention the index cache.
diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index 9e90a4608d..59e3dbf9de 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -557,6 +557,7 @@ PROFILE_CFLAGS = @PROFILE_CFLAGS@
 # when running make.  I.E.: "make CFLAGS=-Wmissing-prototypes".
 CFLAGS = @CFLAGS@
 CXXFLAGS = @CXXFLAGS@
+CPPFLAGS = @CPPFLAGS@
 
 # Set by configure, for e.g. expat.  Python installations are such that
 # C headers are included using their basename (for example, we #include
@@ -564,7 +565,7 @@ CXXFLAGS = @CXXFLAGS@
 # are sometimes a little generic, we think that the risk of collision
 # with other header files is high.  If that happens, we try to mitigate
 # a bit the consequences by putting the Python includes last in the list.
-INTERNAL_CPPFLAGS = @CPPFLAGS@ @GUILE_CPPFLAGS@ @PYTHON_CPPFLAGS@
+INTERNAL_CPPFLAGS = $(CPPFLAGS) @GUILE_CPPFLAGS@ @PYTHON_CPPFLAGS@
 
 # INTERNAL_CFLAGS is the aggregate of all other *CFLAGS macros.
 INTERNAL_CFLAGS_BASE = \