diff --git a/bzip2.c b/bzip2.c
index 1538faf..9ef7536 100644
--- a/bzip2.c
+++ b/bzip2.c
@@ -1767,8 +1767,8 @@ void addFlagsFromEnvVar ( Cell** argList, Char* varName )
          if (p[i] == 0) break;
          p += i;
          i = 0;
-         while (isspace((Int32)(p[0]))) p++;
-         while (p[i] != 0 && !isspace((Int32)(p[i]))) i++;
+         while (isspace((UChar)(p[0]))) p++;
+         while (p[i] != 0 && !isspace((UChar)(p[i]))) i++;
          if (i > 0) {
             k = i; if (k > FILE_NAME_LEN-10) k = FILE_NAME_LEN-10;
             for (j = 0; j < k; j++) tmpName[j] = p[j];
diff --git a/bzlib.c b/bzlib.c
index 2178655..100873c 100644
--- a/bzlib.c
+++ b/bzlib.c
@@ -1408,7 +1408,7 @@ BZFILE * bzopen_or_bzdopen
       case 's':
          smallMode = 1; break;
       default:
-         if (isdigit((int)(*mode))) {
+         if (isdigit((unsigned char)(*mode))) {
             blockSize100k = *mode-BZ_HDR_0;
          }
       }