diff --git a/libutf/isalpharune.c b/libutf/isalpharune.c
index 07811fc..9d1faff 100644
--- a/libutf/isalpharune.c
+++ b/libutf/isalpharune.c
@@ -4,7 +4,7 @@
 #include "../utf.h"
 #include "runetype.h"
 
-static Rune alpha3[][2] = {
+static const Rune alpha3[][2] = {
 	{ 0x00D6, 0x00D8 },
 	{ 0x00F6, 0x00F8 },
 	{ 0x02EC, 0x02EE },
@@ -201,7 +201,7 @@ static Rune alpha3[][2] = {
 	{ 0x1EEA9, 0x1EEAB },
 };
 
-static Rune alpha2[][2] = {
+static const Rune alpha2[][2] = {
 	{ 0x0041, 0x005A },
 	{ 0x0061, 0x007A },
 	{ 0x00C0, 0x00D6 },
@@ -715,7 +715,7 @@ static Rune alpha2[][2] = {
 	{ 0x2F800, 0x2FA1D },
 };
 
-static Rune alpha1[] = {
+static const Rune alpha1[] = {
 	0x00AA,
 	0x00B5,
 	0x00BA,
@@ -818,7 +818,7 @@ static Rune alpha1[] = {
 int
 isalpharune(Rune r)
 {
-	Rune *match;
+	const Rune *match;
 
 	if((match = bsearch(&r, alpha3, nelem(alpha3), sizeof *alpha3, &rune2cmp)))
 		return !((r - match[0]) % 2);
diff --git a/libutf/iscntrlrune.c b/libutf/iscntrlrune.c
index 286dce8..603e57c 100644
--- a/libutf/iscntrlrune.c
+++ b/libutf/iscntrlrune.c
@@ -4,7 +4,7 @@
 #include "../utf.h"
 #include "runetype.h"
 
-static Rune cntrl2[][2] = {
+static const Rune cntrl2[][2] = {
 	{ 0x0000, 0x001F },
 	{ 0x007F, 0x009F },
 };
diff --git a/libutf/isdigitrune.c b/libutf/isdigitrune.c
index 4e58c79..c8901bc 100644
--- a/libutf/isdigitrune.c
+++ b/libutf/isdigitrune.c
@@ -4,7 +4,7 @@
 #include "../utf.h"
 #include "runetype.h"
 
-static Rune digit2[][2] = {
+static const Rune digit2[][2] = {
 	{ 0x0030, 0x0039 },
 	{ 0x0660, 0x0669 },
 	{ 0x06F0, 0x06F9 },
diff --git a/libutf/isspacerune.c b/libutf/isspacerune.c
index bb8fe28..8583f93 100644
--- a/libutf/isspacerune.c
+++ b/libutf/isspacerune.c
@@ -4,14 +4,14 @@
 #include "../utf.h"
 #include "runetype.h"
 
-static Rune space2[][2] = {
+static const Rune space2[][2] = {
 	{ 0x0009, 0x000D },
 	{ 0x001C, 0x0020 },
 	{ 0x2000, 0x200A },
 	{ 0x2028, 0x2029 },
 };
 
-static Rune space1[] = {
+static const Rune space1[] = {
 	0x0085,
 	0x00A0,
 	0x1680,
diff --git a/libutf/istitlerune.c b/libutf/istitlerune.c
index 211a4aa..36b38d1 100644
--- a/libutf/istitlerune.c
+++ b/libutf/istitlerune.c
@@ -4,13 +4,13 @@
 #include "../utf.h"
 #include "runetype.h"
 
-static Rune title2[][2] = {
+static const Rune title2[][2] = {
 	{ 0x1F88, 0x1F8F },
 	{ 0x1F98, 0x1F9F },
 	{ 0x1FA8, 0x1FAF },
 };
 
-static Rune title1[] = {
+static const Rune title1[] = {
 	0x01C5,
 	0x01C8,
 	0x01CB,
diff --git a/libutf/lowerrune.c b/libutf/lowerrune.c
index 3649214..d91a364 100644
--- a/libutf/lowerrune.c
+++ b/libutf/lowerrune.c
@@ -4,7 +4,7 @@
 #include "../utf.h"
 #include "runetype.h"
 
-static Rune lower4[][2] = {
+static const Rune lower4[][2] = {
 	{ 0x0101, 0x012F },
 	{ 0x0133, 0x0137 },
 	{ 0x013A, 0x0148 },
@@ -42,7 +42,7 @@ static Rune lower4[][2] = {
 	{ 0xA7D7, 0xA7D9 },
 };
 
-static Rune lower2[][3] = {
+static const Rune lower2[][3] = {
 	{ 0x0061, 0x007A, 0x0041 },
 	{ 0x00E0, 0x00F6, 0x00C0 },
 	{ 0x00F8, 0x00FE, 0x00D8 },
@@ -161,7 +161,7 @@ static Rune lower2[][3] = {
 	{ 0x1E922, 0x1E943, 0x1E900 },
 };
 
-static Rune lower1[][2] = {
+static const Rune lower1[][2] = {
 	{ 0x00B5, 0x039C },
 	{ 0x00DF, 0x00DF },
 	{ 0x00FF, 0x0178 },
@@ -327,7 +327,7 @@ static Rune lower1[][2] = {
 int
 islowerrune(Rune r)
 {
-	Rune *match;
+	const Rune *match;
 
 	if((match = bsearch(&r, lower4, nelem(lower4), sizeof *lower4, &rune2cmp)))
 		return !((r - match[0]) % 2);
diff --git a/libutf/mkrunetype.awk b/libutf/mkrunetype.awk
index 3736e78..e01ea2c 100644
--- a/libutf/mkrunetype.awk
+++ b/libutf/mkrunetype.awk
@@ -129,7 +129,7 @@ function mkis(name, runev, runec, file, casev, casename) {
 
 	#generate list of laces 1
 	if(rune3c > 0) {
-		print "static Rune "name"3[][2] = {" > file;
+		print "static const Rune "name"3[][2] = {" > file;
 		for(j = 0; j < rune3c; j++) {
 			print "\t{ 0x"rune3v0[j]", 0x"rune3v1[j]" }," > file;
 		}
@@ -138,7 +138,7 @@ function mkis(name, runev, runec, file, casev, casename) {
 
 	#generate list of laces 2
 	if(rune4c > 0) {
-		print "static Rune "name"4[][2] = {" > file;
+		print "static const Rune "name"4[][2] = {" > file;
 		for(j = 0; j < rune4c; j++) {
 			print "\t{ 0x"rune4v0[j]", 0x"rune4v1[j]" }," > file;
 		}
@@ -148,12 +148,12 @@ function mkis(name, runev, runec, file, casev, casename) {
 	# generate list of ranges
 	if(rune2c > 0) {
 		if(length(casev) > 0) {
-			print "static Rune "name"2[][3] = {" > file;
+			print "static const Rune "name"2[][3] = {" > file;
 			for(j = 0; j < rune2c; j++) {
 				print "\t{ 0x"rune2v0[j]", 0x"rune2v1[j]", 0x"case2v[j]" }," > file;
 			}
 		} else {
-			print "static Rune "name"2[][2] = {" > file
+			print "static const Rune "name"2[][2] = {" > file
 			for(j = 0; j < rune2c; j++) {
 				print "\t{ 0x"rune2v0[j]", 0x"rune2v1[j]" }," > file;
 			}
@@ -164,12 +164,12 @@ function mkis(name, runev, runec, file, casev, casename) {
 	# generate list of singletons
 	if(rune1c > 0) {
 		if(length(casev) > 0) {
-			print "static Rune "name"1[][2] = {" > file;
+			print "static const Rune "name"1[][2] = {" > file;
 			for(j = 0; j < rune1c; j++) {
 				print "\t{ 0x"rune1v[j]", 0x"case1v[j]" }," > file;
 			}
 		} else {
-			print "static Rune "name"1[] = {" > file;
+			print "static const Rune "name"1[] = {" > file;
 			for(j = 0; j < rune1c; j++) {
 				print "\t0x"rune1v[j]"," > file;
 			}
@@ -179,7 +179,7 @@ function mkis(name, runev, runec, file, casev, casename) {
 	# generate lookup function
 	print "int\nis"name"rune(Rune r)\n{" > file;
 	if(rune4c > 0 || rune3c > 0)
-		print "\tRune *match;\n" > file;
+		print "\tconst Rune *match;\n" > file;
 	if(rune4c > 0) {
 		print "\tif((match = bsearch(&r, "name"4, nelem("name"4), sizeof *"name"4, &rune2cmp)))" > file;
 		print "\t\treturn !((r - match[0]) % 2);" > file;
diff --git a/libutf/upperrune.c b/libutf/upperrune.c
index accc475..0c874a8 100644
--- a/libutf/upperrune.c
+++ b/libutf/upperrune.c
@@ -4,7 +4,7 @@
 #include "../utf.h"
 #include "runetype.h"
 
-static Rune upper3[][2] = {
+static const Rune upper3[][2] = {
 	{ 0x0100, 0x012E },
 	{ 0x0132, 0x0136 },
 	{ 0x0139, 0x0147 },
@@ -42,7 +42,7 @@ static Rune upper3[][2] = {
 	{ 0xA7D6, 0xA7D8 },
 };
 
-static Rune upper2[][3] = {
+static const Rune upper2[][3] = {
 	{ 0x0041, 0x005A, 0x0061 },
 	{ 0x00C0, 0x00D6, 0x00E0 },
 	{ 0x00D8, 0x00DE, 0x00F8 },
@@ -125,7 +125,7 @@ static Rune upper2[][3] = {
 	{ 0x1E900, 0x1E921, 0x1E922 },
 };
 
-static Rune upper1[][2] = {
+static const Rune upper1[][2] = {
 	{ 0x0130, 0x0069 },
 	{ 0x0178, 0x00FF },
 	{ 0x0181, 0x0253 },
@@ -236,7 +236,7 @@ static Rune upper1[][2] = {
 int
 isupperrune(Rune r)
 {
-	Rune *match;
+	const Rune *match;
 
 	if((match = bsearch(&r, upper3, nelem(upper3), sizeof *upper3, &rune2cmp)))
 		return !((r - match[0]) % 2);