diff --git a/Configure b/Configure
index ef2257f43838..27410e8f759c 100755
--- a/Configure
+++ b/Configure
@@ -1111,6 +1111,7 @@ installprefix=''
 installprefixexp=''
 installstyle=''
 installusrbinperl=''
+intmaxsize=''
 intsize=''
 longsize=''
 shortsize=''
@@ -5787,12 +5788,14 @@ case "$intsize" in
 #ifdef I_STDLIB
 #include <stdlib.h>
 #endif
+#include <stdint.h>
 #include <stdio.h>
 int main()
 {
 	printf("intsize=%d;\n", (int)sizeof(int));
 	printf("longsize=%d;\n", (int)sizeof(long));
 	printf("shortsize=%d;\n", (int)sizeof(short));
+	printf("intmaxsize=%d;\n", (int)sizeof(intmax_t));
 	exit(0);
 }
 EOCP
@@ -5802,6 +5805,7 @@ EOCP
 		echo "Your integers are $intsize bytes long."
 		echo "Your long integers are $longsize bytes long."
 		echo "Your short integers are $shortsize bytes long."
+		echo "Your longest integers are $intmaxsize bytes long."
 	else
 		$cat >&4 <<EOM
 !
@@ -5822,6 +5826,10 @@ EOM
 		rp="What is the size of a short integer (in bytes)?"
 		. ./myread
 		shortsize="$ans"
+		dflt=$longsize
+		rp="What is the size of a intmax_t integer (in bytes)?"
+		. ./myread
+		intmaxsize="$ans"
 	fi
 	;;
 esac
@@ -24264,7 +24272,7 @@ $rm_try
 set i_stdckdint
 eval $setvar
 
-: see if stdint is available
+: stdint.h should be available, but this makes sure it gets in config.h
 set stdint.h i_stdint
 eval $inhdr
 
@@ -25753,6 +25761,7 @@ installvendorlib='$installvendorlib'
 installvendorman1dir='$installvendorman1dir'
 installvendorman3dir='$installvendorman3dir'
 installvendorscript='$installvendorscript'
+intmaxsize='$intmaxsize'
 intsize='$intsize'
 issymlink='$issymlink'
 ivdformat='$ivdformat'
diff --git a/Cross/config.sh-arm-linux b/Cross/config.sh-arm-linux
index 0fcf0a0b4645..c43bfdeb936c 100644
--- a/Cross/config.sh-arm-linux
+++ b/Cross/config.sh-arm-linux
@@ -868,6 +868,7 @@ installvendorlib=''
 installvendorman1dir=''
 installvendorman3dir=''
 installvendorscript=''
+intmaxsize='8'
 intsize='4'
 issymlink='/usr/bin/test -h'
 ivdformat='"ld"'
diff --git a/Cross/config.sh-arm-linux-n770 b/Cross/config.sh-arm-linux-n770
index 18607ad0ff73..4621ecfb27b1 100644
--- a/Cross/config.sh-arm-linux-n770
+++ b/Cross/config.sh-arm-linux-n770
@@ -866,6 +866,7 @@ installvendorlib=''
 installvendorman1dir=''
 installvendorman3dir=''
 installvendorscript=''
+intmaxsize='8'
 intsize='4'
 issymlink='/usr/bin/test -h'
 ivdformat='"ld"'
diff --git a/Porting/Glossary b/Porting/Glossary
index abea6f9acb64..85e5823c3dc4 100644
--- a/Porting/Glossary
+++ b/Porting/Glossary
@@ -4134,6 +4134,10 @@ installvendorscript (vendorscript.U):
 	those systems using AFS. For extra portability, only this variable
 	should be used in makefiles.
 
+intmaxsize (intsize.U):
+	This variable contains the value of the INTMAXSIZE symbol, which
+	indicates to the C program how many bytes there are in intmax_t.
+
 intsize (intsize.U):
 	This variable contains the value of the INTSIZE symbol, which
 	indicates to the C program how many bytes there are in an int.
diff --git a/Porting/config.sh b/Porting/config.sh
index 41e0e490b3f0..b5390d68e037 100644
--- a/Porting/config.sh
+++ b/Porting/config.sh
@@ -892,6 +892,7 @@ installvendorlib=''
 installvendorman1dir=''
 installvendorman3dir=''
 installvendorscript=''
+intmaxsize='8'
 intsize='4'
 issymlink='test -h'
 ivdformat='"ld"'
diff --git a/config_h.SH b/config_h.SH
index 9f7082e9c614..124710fee389 100755
--- a/config_h.SH
+++ b/config_h.SH
@@ -799,9 +799,14 @@ sed <<!GROK!THIS! >$CONFIG_H -e 's!^#undef\(.*/\)\*!/\*#define\1 \*!' -e 's!^#un
  *	This symbol contains the value of sizeof(short) so that the C
  *	preprocessor can make decisions based on it.
  */
+/* INTMAXSIZE:
+ *	This symbol contains the value of sizeof(intmax_t) so that the C
+ *	preprocessor can make decisions based on it.
+ */
 #define INTSIZE $intsize		/**/
 #define LONGSIZE $longsize		/**/
 #define SHORTSIZE $shortsize		/**/
+#define INTMAXSIZE $intmaxsize		/**/
 
 /* MULTIARCH:
  *	This symbol, if defined, signifies that the build
diff --git a/configure.com b/configure.com
index f800aecc6ea0..16ec73f2cf30 100644
--- a/configure.com
+++ b/configure.com
@@ -3263,6 +3263,7 @@ $ OS
 $ WS "#if defined(__DECC) || defined(__DECCXX)"
 $ WS "#include <stdlib.h>"
 $ WS "#endif"
+$ WS "#include <stdint.h>"
 $ WS "#include <stdio.h>"
 $ WS "int main()"
 $ WS "{"
@@ -5574,6 +5575,10 @@ $   gosub type_size_check
 $   intsize = tmp
 $ ENDIF
 $!
+$ tmp = "''intmax_t'"
+$ gosub type_size_check
+$ intmaxsize = tmp
+$!
 $ tmp = "''u32type'"
 $ gosub type_size_check
 $ u32size = tmp
@@ -6615,6 +6620,7 @@ $ WC "installsitearch='" + installsitearch + "'"
 $ WC "installsitebin='" + sitebin + "'"
 $ WC "installsitelib='" + installsitelib + "'"
 $ WC "installusrbinperl='undef'"
+$ WC "intmaxsize='" + intmaxsize + "'"
 $ WC "intsize='" + intsize + "'"
 $ WC "ivdformat='" + ivdformat + "'"
 $ WC "ivsize='" + ivsize + "'"
diff --git a/plan9/config_sh.sample b/plan9/config_sh.sample
index 3da90256ec4a..9b142bd8aab1 100644
--- a/plan9/config_sh.sample
+++ b/plan9/config_sh.sample
@@ -850,6 +850,7 @@ installusrbinperl='undef'
 installvendorarch=''
 installvendorbin=''
 installvendorlib=''
+intmaxsize='8'
 intsize='4'
 issymlink='/bin/test -h'
 ivdformat='"ld"'
diff --git a/win32/config.gc b/win32/config.gc
index 017c14d30abc..756fc2f406bc 100644
--- a/win32/config.gc
+++ b/win32/config.gc
@@ -862,6 +862,7 @@ installvendorlib=''
 installvendorman1dir=''
 installvendorman3dir=''
 installvendorscript=''
+intmaxsize='8'
 intsize='4'
 issymlink=''
 ivdformat='"ld"'
diff --git a/win32/config.vc b/win32/config.vc
index 77351781cdc7..b13e276ff74d 100644
--- a/win32/config.vc
+++ b/win32/config.vc
@@ -861,6 +861,7 @@ installvendorlib=''
 installvendorman1dir=''
 installvendorman3dir=''
 installvendorscript=''
+intmaxsize='8'
 intsize='4'
 issymlink=''
 ivdformat='"ld"'