diff --git a/pnm2ppa.c b/pnm2ppa.c
index 4ae36ce..0d60fbb 100644
--- a/pnm2ppa.c
+++ b/pnm2ppa.c
@@ -604,7 +604,7 @@ main (int argc, char *argv[])
   int i, opt_index;
   FILE *in = NULL, *out = NULL, *gf = NULL;
   struct stat tmpstat;
-  char c;
+  int c;
   BOOLEAN get_Gamma = true;
 
   char *gammaFile=NULL;