diff --git a/libguile/chars.c b/libguile/chars.c
index 56239f597..552a2d9c1 100644
--- a/libguile/chars.c
+++ b/libguile/chars.c
@@ -363,7 +363,7 @@ static const scm_t_uint32 const scm_alt_charnums[] = {
 const char *
 scm_i_charname (SCM chr)
 {
-  int c;
+  size_t c;
   scm_t_uint32 i = SCM_CHAR (chr);
 
   for (c = 0; c < SCM_N_R5RS_CHARNAMES; c++)
@@ -385,7 +385,7 @@ scm_i_charname (SCM chr)
 SCM
 scm_i_charname_to_char (const char *charname, size_t charname_len)
 {
-  int c;
+  size_t c;
 
   /* The R5RS charnames.  These are supposed to be case
      insensitive. */
diff --git a/libguile/chars.h b/libguile/chars.h
index e016cb28e..51adc21e5 100644
--- a/libguile/chars.h
+++ b/libguile/chars.h
@@ -32,9 +32,9 @@
 #define SCM_CHARP(x) (SCM_ITAG8(x) == scm_tc8_char)
 #define SCM_CHAR(x) ((scm_t_wchar)SCM_ITAG8_DATA(x))
 
-#define SCM_MAKE_CHAR(x)                                              \
-  ((x) < 0                                                            \
-   ? SCM_MAKE_ITAG8 ((scm_t_bits) (unsigned char) (x), scm_tc8_char)  \
+#define SCM_MAKE_CHAR(x)                                               \
+  ((scm_t_int32) (x) < 0                                               \
+   ? SCM_MAKE_ITAG8 ((scm_t_bits) (unsigned char) (x), scm_tc8_char)   \
    : SCM_MAKE_ITAG8 ((scm_t_bits) (x), scm_tc8_char))
 
 #define SCM_CODEPOINT_MAX (0x10ffff)