diff --git a/Makefile.pre.in b/Makefile.pre.in
index 31efecacb30..132116260bf 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -58,6 +58,8 @@ INSTALL_DATA=	@INSTALL_DATA@
 # Also, making them read-only seems to be a good idea...
 INSTALL_SHARED= ${INSTALL} -m 555
 
+MKDIR_P=	@MKDIR_P@
+
 MAKESETUP=      $(srcdir)/Modules/makesetup
 
 # Compiler options
@@ -233,6 +235,18 @@ LIBFFI_INCLUDEDIR=	@LIBFFI_INCLUDEDIR@
 # Parser
 PGEN=		Parser/pgen$(EXE)
 
+PSRCS=		\
+		Parser/acceler.c \
+		Parser/grammar1.c \
+		Parser/listnode.c \
+		Parser/node.c \
+		Parser/parser.c \
+		Parser/bitset.c \
+		Parser/metagrammar.c \
+		Parser/firstsets.c \
+		Parser/grammar.c \
+		Parser/pgen.c
+
 POBJS=		\
 		Parser/acceler.o \
 		Parser/grammar1.o \
@@ -247,6 +261,16 @@ POBJS=		\
 
 PARSER_OBJS=	$(POBJS) Parser/myreadline.o Parser/parsetok.o Parser/tokenizer.o
 
+PGSRCS=		\
+		Objects/obmalloc.c \
+		Python/dynamic_annotations.c \
+		Python/mysnprintf.c \
+		Python/pyctype.c \
+		Parser/tokenizer_pgen.c \
+		Parser/printgrammar.c \
+		Parser/parsetok_pgen.c \
+		Parser/pgenmain.c
+
 PGOBJS=		\
 		Objects/obmalloc.o \
 		Python/dynamic_annotations.o \
@@ -262,7 +286,8 @@ PARSER_HEADERS= \
 		$(srcdir)/Include/parsetok.h \
 		$(srcdir)/Parser/tokenizer.h
 
-PGENOBJS=	$(PGENMAIN) $(POBJS) $(PGOBJS)
+PGENSRCS=	$(PSRCS) $(PGSRCS)
+PGENOBJS=	$(POBJS) $(PGOBJS)
 
 ##########################################################################
 # AST
@@ -591,12 +616,13 @@ Python/sysmodule.o: $(srcdir)/Python/sysmodule.c Makefile
 
 $(IO_OBJS): $(IO_H)
 
-# Use a stamp file to prevent make -j invoking pgen twice
-$(GRAMMAR_H) $(GRAMMAR_C): Parser/pgen.stamp
-Parser/pgen.stamp: $(PGEN) $(GRAMMAR_INPUT)
-		-@$(INSTALL) -d Include
+$(GRAMMAR_H): $(GRAMMAR_INPUT) $(PGENSRCS)
+		@$(MKDIR_P) Include
+		$(MAKE) $(PGEN)
 		$(PGEN) $(GRAMMAR_INPUT) $(GRAMMAR_H) $(GRAMMAR_C)
-		-touch Parser/pgen.stamp
+$(GRAMMAR_C): $(GRAMMAR_H) $(GRAMMAR_INPUT) $(PGENSRCS)
+		$(MAKE) $(GRAMMAR_H)
+		touch $(GRAMMAR_C)
 
 $(PGEN):	$(PGENOBJS)
 		$(CC) $(OPT) $(PY_LDFLAGS) $(PGENOBJS) $(LIBS) -o $(PGEN)
diff --git a/Misc/NEWS b/Misc/NEWS
index cb1ec6ddd4d..d41a2b4e41c 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -106,6 +106,11 @@ Library
 - Issue #14210: pdb now has tab-completion not only for command names, but
   also for their arguments, wherever possible.
 
+Build
+-----
+
+- Issue #14321: Do not run pgen during the build if files are up to date.
+
 Extension Modules
 -----------------
 
diff --git a/configure b/configure
index 7abf15b01b1..a71e128cbf1 100755
--- a/configure
+++ b/configure
@@ -640,6 +640,7 @@ BASECFLAGS
 OPT
 ABIFLAGS
 LN
+MKDIR_P
 INSTALL_DATA
 INSTALL_SCRIPT
 INSTALL_PROGRAM
@@ -5382,6 +5383,48 @@ test -z "$INSTALL_SCRIPT" && INSTALL_SCRIPT='${INSTALL}'
 
 test -z "$INSTALL_DATA" && INSTALL_DATA='${INSTALL} -m 644'
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for a thread-safe mkdir -p" >&5
+$as_echo_n "checking for a thread-safe mkdir -p... " >&6; }
+if test -z "$MKDIR_P"; then
+  if ${ac_cv_path_mkdir+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH$PATH_SEPARATOR/opt/sfw/bin
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_prog in mkdir gmkdir; do
+	 for ac_exec_ext in '' $ac_executable_extensions; do
+	   { test -f "$as_dir/$ac_prog$ac_exec_ext" && $as_test_x "$as_dir/$ac_prog$ac_exec_ext"; } || continue
+	   case `"$as_dir/$ac_prog$ac_exec_ext" --version 2>&1` in #(
+	     'mkdir (GNU coreutils) '* | \
+	     'mkdir (coreutils) '* | \
+	     'mkdir (fileutils) '4.1*)
+	       ac_cv_path_mkdir=$as_dir/$ac_prog$ac_exec_ext
+	       break 3;;
+	   esac
+	 done
+       done
+  done
+IFS=$as_save_IFS
+
+fi
+
+  test -d ./--version && rmdir ./--version
+  if test "${ac_cv_path_mkdir+set}" = set; then
+    MKDIR_P="$ac_cv_path_mkdir -p"
+  else
+    # As a last resort, use the slow shell script.  Don't cache a
+    # value for MKDIR_P within a source directory, because that will
+    # break other packages using the cache if that directory is
+    # removed, or if the value is a relative name.
+    MKDIR_P="$ac_install_sh -d"
+  fi
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $MKDIR_P" >&5
+$as_echo "$MKDIR_P" >&6; }
+
 
 # Not every filesystem supports hard links
 
@@ -14647,6 +14690,7 @@ gives unlimited permission to copy, distribute and modify it."
 ac_pwd='$ac_pwd'
 srcdir='$srcdir'
 INSTALL='$INSTALL'
+MKDIR_P='$MKDIR_P'
 test -n "\$AWK" || AWK=awk
 _ACEOF
 
@@ -15214,6 +15258,11 @@ ac_abs_srcdir=$ac_abs_top_srcdir$ac_dir_suffix
   [\\/$]* | ?:[\\/]* ) ac_INSTALL=$INSTALL ;;
   *) ac_INSTALL=$ac_top_build_prefix$INSTALL ;;
   esac
+  ac_MKDIR_P=$MKDIR_P
+  case $MKDIR_P in
+  [\\/$]* | ?:[\\/]* ) ;;
+  */*) ac_MKDIR_P=$ac_top_build_prefix$MKDIR_P ;;
+  esac
 _ACEOF
 
 cat >>$CONFIG_STATUS <<\_ACEOF || ac_write_fail=1
@@ -15268,6 +15317,7 @@ s&@builddir@&$ac_builddir&;t t
 s&@abs_builddir@&$ac_abs_builddir&;t t
 s&@abs_top_builddir@&$ac_abs_top_builddir&;t t
 s&@INSTALL@&$ac_INSTALL&;t t
+s&@MKDIR_P@&$ac_MKDIR_P&;t t
 $ac_datarootdir_hack
 "
 eval sed \"\$ac_sed_extra\" "$ac_file_inputs" | $AWK -f "$ac_tmp/subs.awk" \
diff --git a/configure.ac b/configure.ac
index 47ba787a514..a38a5ccf4fd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -848,6 +848,7 @@ bsdos*|hp*|HP*)
 	fi
 esac
 AC_PROG_INSTALL
+AC_PROG_MKDIR_P
 
 # Not every filesystem supports hard links
 AC_SUBST(LN)