diff --git a/compiler/libpc300/sc1.c b/compiler/libpc300/sc1.c
index 9fe5f005..f261d642 100755
--- a/compiler/libpc300/sc1.c
+++ b/compiler/libpc300/sc1.c
@@ -1456,7 +1456,7 @@ static void setconstants(void)
   #endif
   add_constant("charbits",sCHARBITS,sGLOBAL,0);
   add_constant("charmin",0,sGLOBAL,0);
-  add_constant("charmax",~(-1 << sCHARBITS) - 1,sGLOBAL,0);
+  add_constant("charmax",~(-1UL << sCHARBITS) - 1,sGLOBAL,0);
   add_constant("ucharmax",(1 << (sizeof(cell)-1)*8)-1,sGLOBAL,0);
 
   add_constant("__Pawn",VERSION_INT,sGLOBAL,0);
diff --git a/compiler/libpc300/sc3.c b/compiler/libpc300/sc3.c
index 1cc436ed..e7bc320f 100755
--- a/compiler/libpc300/sc3.c
+++ b/compiler/libpc300/sc3.c
@@ -749,7 +749,7 @@ static int hier14(value *lval1)
    * negative value would do).
    */
   for (i=0; i<sDIMEN_MAX; i++)
-    arrayidx1[i]=arrayidx2[i]=(cell)(-1L << (sizeof(cell)*8-1));
+    arrayidx1[i]=arrayidx2[i]=(cell)(-1UL << (sizeof(cell)*8-1));
   org_arrayidx=lval1->arrayidx; /* save current pointer, to reset later */
   if (lval1->arrayidx==NULL)
     lval1->arrayidx=arrayidx1;
diff --git a/third_party/zlib/inflate.c b/third_party/zlib/inflate.c
index 870f89bb..2f78dc49 100644
--- a/third_party/zlib/inflate.c
+++ b/third_party/zlib/inflate.c
@@ -1504,7 +1504,7 @@ z_streamp strm;
 {
     struct inflate_state FAR *state;
 
-    if (strm == Z_NULL || strm->state == Z_NULL) return -1L << 16;
+    if (strm == Z_NULL || strm->state == Z_NULL) return -1UL << 16;
     state = (struct inflate_state FAR *)strm->state;
     return ((long)(state->back) << 16) +
         (state->mode == COPY ? state->length :