diff --git a/include/qrintf.h b/include/qrintf.h
index 986f0df..784de9b 100644
--- a/include/qrintf.h
+++ b/include/qrintf.h
@@ -443,28 +443,28 @@ static inline qrintf_chk_t _qrintf_chk_long_long_core(qrintf_chk_t ctx, int fill
     return ctx;
 }
 
-static inline qrintf_nck_t _qrintf_nck_hhd(qrintf_nck_t ctx, char v)
+static inline qrintf_nck_t _qrintf_nck_hhd(qrintf_nck_t ctx, signed char v)
 {
     unsigned char val = v >= 0 ? v : -(unsigned char)v;
     int sign = v < 0;
-    if (sizeof(char) < sizeof(long long)) {
+    if (sizeof(signed char) < sizeof(long long)) {
         return _qrintf_nck_long_core(ctx, 0, 0, (unsigned long)val, sign);
     }
     else {
-        assert(sizeof(char) == sizeof(long long));
+        assert(sizeof(signed char) == sizeof(long long));
         return _qrintf_nck_long_long_core(ctx, 0, 0, (unsigned long long)val, sign);
     }
 }
 
-static inline qrintf_nck_t _qrintf_nck_width_hhd(qrintf_nck_t ctx, int fill_ch, int width, char v)
+static inline qrintf_nck_t _qrintf_nck_width_hhd(qrintf_nck_t ctx, int fill_ch, int width, signed char v)
 {
     unsigned char val = v >= 0 ? v : -(unsigned char)v;
     int sign = v < 0;
-    if (sizeof(char) < sizeof(long long)) {
+    if (sizeof(signed char) < sizeof(long long)) {
         return _qrintf_nck_long_core(ctx, fill_ch, width, (unsigned long)val, sign);
     }
     else {
-        assert(sizeof(char) == sizeof(long long));
+        assert(sizeof(signed char) == sizeof(long long));
         return _qrintf_nck_long_long_core(ctx, fill_ch, width, (unsigned long long)val, sign);
     }
 }
@@ -993,28 +993,28 @@ static inline qrintf_nck_t _qrintf_nck_width_zx(qrintf_nck_t ctx, int fill_ch, i
     return ctx;
 }
 
-static inline qrintf_chk_t _qrintf_chk_hhd(qrintf_chk_t ctx, char v)
+static inline qrintf_chk_t _qrintf_chk_hhd(qrintf_chk_t ctx, signed char v)
 {
     unsigned char val = v >= 0 ? v : -(unsigned char)v;
     int sign = v < 0;
-    if (sizeof(char) < sizeof(long long)) {
+    if (sizeof(signed char) < sizeof(long long)) {
         return _qrintf_chk_long_core(ctx, 0, 0, (unsigned long)val, sign);
     }
     else {
-        assert(sizeof(char) == sizeof(long long));
+        assert(sizeof(signed char) == sizeof(long long));
         return _qrintf_chk_long_long_core(ctx, 0, 0, (unsigned long long)val, sign);
     }
 }
 
-static inline qrintf_chk_t _qrintf_chk_width_hhd(qrintf_chk_t ctx, int fill_ch, int width, char v)
+static inline qrintf_chk_t _qrintf_chk_width_hhd(qrintf_chk_t ctx, int fill_ch, int width, signed char v)
 {
     unsigned char val = v >= 0 ? v : -(unsigned char)v;
     int sign = v < 0;
-    if (sizeof(char) < sizeof(long long)) {
+    if (sizeof(signed char) < sizeof(long long)) {
         return _qrintf_chk_long_core(ctx, fill_ch, width, (unsigned long)val, sign);
     }
     else {
-        assert(sizeof(char) == sizeof(long long));
+        assert(sizeof(signed char) == sizeof(long long));
         return _qrintf_chk_long_long_core(ctx, fill_ch, width, (unsigned long long)val, sign);
     }
 }
diff --git a/misc/gen-qrintf.h.pl b/misc/gen-qrintf.h.pl
index bb821e7..7ba1b5f 100755
--- a/misc/gen-qrintf.h.pl
+++ b/misc/gen-qrintf.h.pl
@@ -27,9 +27,11 @@
 sub build_d {
     return build_mt(template => << 'EOT', escape_func => undef)->(@_);
 ? my ($check, $type, $suffix) = @_;
+? my $unsigned_type = $type;
+? $unsigned_type =~ s/^(signed )?/unsigned /g;
 static inline qrintf_<?= $check ?>_t _qrintf_<?= $check ?>_<?= $suffix ?>(qrintf_<?= $check ?>_t ctx, <?= $type ?> v)
 {
-    unsigned <?= $type ?> val = v >= 0 ? v : -(unsigned <?= $type ?>)v;
+    <?= $unsigned_type ?> val = v >= 0 ? v : -(<?= $unsigned_type ?>)v;
     int sign = v < 0;
     if (sizeof(<?= $type ?>) < sizeof(long long)) {
         return _qrintf_<?= $check ?>_long_core(ctx, 0, 0, (unsigned long)val, sign);
@@ -42,7 +44,7 @@ sub build_d {
 
 static inline qrintf_<?= $check ?>_t _qrintf_<?= $check ?>_width_<?= $suffix ?>(qrintf_<?= $check ?>_t ctx, int fill_ch, int width, <?= $type ?> v)
 {
-    unsigned <?= $type ?> val = v >= 0 ? v : -(unsigned <?= $type ?>)v;
+    <?= $unsigned_type ?> val = v >= 0 ? v : -(<?= $unsigned_type ?>)v;
     int sign = v < 0;
     if (sizeof(<?= $type ?>) < sizeof(long long)) {
         return _qrintf_<?= $check ?>_long_core(ctx, fill_ch, width, (unsigned long)val, sign);
@@ -564,7 +566,7 @@ sub build_x {
 }
 
 ? for my $check (qw(nck chk)) {
-<?= $build_d->($check, "char", "hhd") ?>
+<?= $build_d->($check, "signed char", "hhd") ?>
 <?= $build_d->($check, "short", "hd") ?>
 <?= $build_d->($check, "int", "d",) ?>
 <?= $build_d->($check, "long", "ld") ?>