diff --git a/simgear/nasal/iolib.c b/simgear/nasal/iolib.c
index c08296a9..16d31338 100644
--- a/simgear/nasal/iolib.c
+++ b/simgear/nasal/iolib.c
@@ -143,7 +143,7 @@ static naRef f_open(naContext c, naRef me, int argc, naRef* args)
 // frees buffer before tossing an error
 static int getcguard(naContext ctx, FILE* f, void* buf)
 {
-    char c;
+    int c;
     naModUnlock(); c = fgetc(f); naModLock();
     if(ferror(f)) {
         naFree(buf);
@@ -159,8 +159,8 @@ static naRef f_readln(naContext ctx, naRef me, int argc, naRef* args)
 {
     naRef result;
     struct naIOGhost* g = argc==1 ? ioghost(args[0]) : 0;
-    int i=0, sz = 128;
-    char c, *buf;
+    int i=0, sz = 128, c, c2;
+    char *buf;
     if(!g || g->type != &naStdIOType)
         naRuntimeError(ctx, "bad argument to readln()");
     buf = naAlloc(sz);
@@ -168,7 +168,7 @@ static naRef f_readln(naContext ctx, naRef me, int argc, naRef* args)
         c = getcguard(ctx, g->handle, buf);
         if(c == EOF || c == '\n') break;
         if(c == '\r') {
-            char c2 = getcguard(ctx, g->handle, buf);
+            c2 = getcguard(ctx, g->handle, buf);
             if(c2 != EOF && c2 != '\n')
                 if(EOF == ungetc(c2, g->handle))
                     break;