diff --git a/database/DBundo.c b/database/DBundo.c
index 56a6bc94..73b98414 100644
--- a/database/DBundo.c
+++ b/database/DBundo.c
@@ -260,7 +260,7 @@ dbUndoSplitForw(us)
 {
     /* Create internal fracture */
     if (dbUndoLastCell == NULL) return;
-    DBSplitTile(dbUndoLastCell->cd_planes[us->sue_plane], &us->sue_point,
+    DBSplitTile(dbUndoLastCell->cd_planes[(unsigned char)us->sue_plane], &us->sue_point,
 		us->sue_splitx);
 }
 
@@ -276,7 +276,7 @@ dbUndoSplitBack(us)
     srect.r_ur.p_y = us->sue_point.p_y + 1;
 
     /* Remove internal fracture and restore original split tile */
-    DBMergeNMTiles0(dbUndoLastCell->cd_planes[us->sue_plane], &srect,
+    DBMergeNMTiles0(dbUndoLastCell->cd_planes[(unsigned char)us->sue_plane], &srect,
 		(PaintUndoInfo *)NULL, TRUE);
 }
 
@@ -314,20 +314,20 @@ dbUndoPaintForw(up)
 	loctype = (up->pue_oldtype & TT_LEFTMASK);
 	dinfo = TT_DIAGONAL | (up->pue_oldtype & TT_DIRECTION);
 
-	DBNMPaintPlane(dbUndoLastCell->cd_planes[up->pue_plane],
-		dinfo, &up->pue_rect, DBStdEraseTbl(loctype, up->pue_plane),
+	DBNMPaintPlane(dbUndoLastCell->cd_planes[(unsigned char)up->pue_plane],
+		dinfo, &up->pue_rect, DBStdEraseTbl(loctype, (unsigned char)up->pue_plane),
 		(PaintUndoInfo *) NULL);
 
 	loctype = (up->pue_oldtype & TT_RIGHTMASK) >> 14;
 	dinfo |= TT_SIDE;
 
-	DBNMPaintPlane(dbUndoLastCell->cd_planes[up->pue_plane],
-		dinfo, &up->pue_rect, DBStdEraseTbl(loctype, up->pue_plane),
+	DBNMPaintPlane(dbUndoLastCell->cd_planes[(unsigned char)up->pue_plane],
+		dinfo, &up->pue_rect, DBStdEraseTbl(loctype, (unsigned char)up->pue_plane),
 		(PaintUndoInfo *) NULL);
     }
     else
-	DBPaintPlane(dbUndoLastCell->cd_planes[up->pue_plane], &up->pue_rect,
-			DBStdEraseTbl(up->pue_oldtype, up->pue_plane),
+	DBPaintPlane(dbUndoLastCell->cd_planes[(unsigned char)up->pue_plane], &up->pue_rect,
+			DBStdEraseTbl(up->pue_oldtype, (unsigned char)up->pue_plane),
 			(PaintUndoInfo *) NULL);
 
     if (up->pue_newtype & TT_DIAGONAL)
@@ -335,20 +335,20 @@ dbUndoPaintForw(up)
 	loctype = (up->pue_newtype & TT_LEFTMASK);
 	dinfo = TT_DIAGONAL | (up->pue_newtype & TT_DIRECTION);
 
-	DBNMPaintPlane(dbUndoLastCell->cd_planes[up->pue_plane],
-		dinfo, &up->pue_rect, DBStdPaintTbl(loctype, up->pue_plane),
+	DBNMPaintPlane(dbUndoLastCell->cd_planes[(unsigned char)up->pue_plane],
+		dinfo, &up->pue_rect, DBStdPaintTbl(loctype, (unsigned char)up->pue_plane),
 		(PaintUndoInfo *) NULL);
 
 	loctype = (up->pue_newtype & TT_RIGHTMASK) >> 14;
 	dinfo |= TT_SIDE;
 
-	DBNMPaintPlane(dbUndoLastCell->cd_planes[up->pue_plane],
-		dinfo, &up->pue_rect, DBStdPaintTbl(loctype, up->pue_plane),
+	DBNMPaintPlane(dbUndoLastCell->cd_planes[(unsigned char)up->pue_plane],
+		dinfo, &up->pue_rect, DBStdPaintTbl(loctype, (unsigned char)up->pue_plane),
 		(PaintUndoInfo *) NULL);
     }
     else
-	DBPaintPlane(dbUndoLastCell->cd_planes[up->pue_plane], &up->pue_rect,
-			DBStdPaintTbl(up->pue_newtype, up->pue_plane),
+	DBPaintPlane(dbUndoLastCell->cd_planes[(unsigned char)up->pue_plane], &up->pue_rect,
+			DBStdPaintTbl(up->pue_newtype, (unsigned char)up->pue_plane),
 			(PaintUndoInfo *) NULL);
 endPaintFor:
     dbUndoUndid = TRUE;
@@ -368,20 +368,20 @@ dbUndoPaintBack(up)
 	loctype = (up->pue_newtype & TT_LEFTMASK);
 	dinfo = TT_DIAGONAL | (up->pue_newtype & TT_DIRECTION);
 
-	DBNMPaintPlane(dbUndoLastCell->cd_planes[up->pue_plane],
-		dinfo, &up->pue_rect, DBStdEraseTbl(loctype, up->pue_plane),
+	DBNMPaintPlane(dbUndoLastCell->cd_planes[(unsigned char)up->pue_plane],
+		dinfo, &up->pue_rect, DBStdEraseTbl(loctype, (unsigned char)up->pue_plane),
 		(PaintUndoInfo *) NULL);
 
 	loctype = (up->pue_newtype & TT_RIGHTMASK) >> 14;
 	dinfo |= TT_SIDE;
 
-	DBNMPaintPlane(dbUndoLastCell->cd_planes[up->pue_plane],
-		dinfo, &up->pue_rect, DBStdEraseTbl(loctype, up->pue_plane),
+	DBNMPaintPlane(dbUndoLastCell->cd_planes[(unsigned char)up->pue_plane],
+		dinfo, &up->pue_rect, DBStdEraseTbl(loctype, (unsigned char)up->pue_plane),
 		(PaintUndoInfo *) NULL);
     }
     else
-	DBPaintPlane(dbUndoLastCell->cd_planes[up->pue_plane], &up->pue_rect,
-			DBStdEraseTbl(up->pue_newtype, up->pue_plane),
+	DBPaintPlane(dbUndoLastCell->cd_planes[(unsigned char)up->pue_plane], &up->pue_rect,
+			DBStdEraseTbl(up->pue_newtype, (unsigned char)up->pue_plane),
 			(PaintUndoInfo *) NULL);
 
     if (up->pue_oldtype & TT_DIAGONAL)
@@ -389,23 +389,23 @@ dbUndoPaintBack(up)
 	loctype = (up->pue_oldtype & TT_LEFTMASK);
 	dinfo = TT_DIAGONAL | (up->pue_oldtype & TT_DIRECTION);
 
-	DBNMPaintPlane(dbUndoLastCell->cd_planes[up->pue_plane], dinfo,
-		&up->pue_rect, DBStdPaintTbl(loctype, up->pue_plane),
+	DBNMPaintPlane(dbUndoLastCell->cd_planes[(unsigned char)up->pue_plane], dinfo,
+		&up->pue_rect, DBStdPaintTbl(loctype, (unsigned char)up->pue_plane),
 		(PaintUndoInfo *) NULL);
 
 	loctype = (up->pue_oldtype & TT_RIGHTMASK) >> 14;
 	dinfo |= TT_SIDE;
 
-	DBNMPaintPlane(dbUndoLastCell->cd_planes[up->pue_plane], dinfo,
-		&up->pue_rect, DBStdPaintTbl(loctype, up->pue_plane),
+	DBNMPaintPlane(dbUndoLastCell->cd_planes[(unsigned char)up->pue_plane], dinfo,
+		&up->pue_rect, DBStdPaintTbl(loctype, (unsigned char)up->pue_plane),
 		(PaintUndoInfo *) NULL);
 
-	DBMergeNMTiles0(dbUndoLastCell->cd_planes[up->pue_plane],
+	DBMergeNMTiles0(dbUndoLastCell->cd_planes[(unsigned char)up->pue_plane],
 		&up->pue_rect, (PaintUndoInfo *)NULL, TRUE);
     }
     else
-	DBPaintPlane(dbUndoLastCell->cd_planes[up->pue_plane], &up->pue_rect,
-			DBStdPaintTbl(up->pue_oldtype, up->pue_plane),
+	DBPaintPlane(dbUndoLastCell->cd_planes[(unsigned char)up->pue_plane], &up->pue_rect,
+			DBStdPaintTbl(up->pue_oldtype, (unsigned char)up->pue_plane),
 			(PaintUndoInfo *) NULL);
 
 endPaintBack:
diff --git a/extflat/EFbuild.c b/extflat/EFbuild.c
index 684f2895..20c31830 100644
--- a/extflat/EFbuild.c
+++ b/extflat/EFbuild.c
@@ -1045,7 +1045,7 @@ efBuildDevice(def, class, type, r, argc, argv)
 		 && (ttype != extGetDevType(EFDevTypes[newdev->dev_type]))))
 	{
 	    TxError("Device %s %s at (%d, %d) overlaps incompatible device %s %s!\n",
-		    extDevTable[class], type, r->r_xbot, r->r_ybot,
+		    extDevTable[(unsigned char)class], type, r->r_xbot, r->r_ybot,
 		    extDevTable[newdev->dev_class], EFDevTypes[newdev->dev_type]);
 	    return 0;
 	}
@@ -1053,7 +1053,7 @@ efBuildDevice(def, class, type, r, argc, argv)
 	{
 	    TxError("Device %s %s at (%d, %d) overlaps device with incompatible"
 		    " number of terminals (%d vs. %d)!\n",
-		    extDevTable[class], type, r->r_xbot, r->r_ybot, nterminals,
+		    extDevTable[(unsigned char)class], type, r->r_xbot, r->r_ybot, nterminals,
 		    newdev->dev_nterm);
 	    return 0;
 	}
diff --git a/extract/ExtBasic.c b/extract/ExtBasic.c
index a776b893..2c73d98c 100644
--- a/extract/ExtBasic.c
+++ b/extract/ExtBasic.c
@@ -2355,7 +2355,7 @@ extOutputDevices(def, transList, outFile)
 	{
 	    case DEV_FET:	/* old style, perimeter & area */
 		fprintf(outFile, "%s %s",
-			extDevTable[devptr->exts_deviceClass],
+			extDevTable[(unsigned char)devptr->exts_deviceClass],
 			devptr->exts_deviceName);
 
 		fprintf(outFile, " %d %d %d %d",
@@ -2490,7 +2490,7 @@ extOutputDevices(def, transList, outFile)
 
 		devptr = extDevFindParamMatch(devptr, length, width);
 		fprintf(outFile, "%s %s",
-			extDevTable[devptr->exts_deviceClass],
+			extDevTable[(unsigned char)devptr->exts_deviceClass],
 			devptr->exts_deviceName);
 
 		fprintf(outFile, " %d %d %d %d",
@@ -2516,7 +2516,7 @@ extOutputDevices(def, transList, outFile)
 	    case DEV_PDIODE:
 		devptr = extDevFindParamMatch(devptr, length, width);
 		fprintf(outFile, "%s %s",
-			extDevTable[devptr->exts_deviceClass],
+			extDevTable[(unsigned char)devptr->exts_deviceClass],
 			devptr->exts_deviceName);
 
 		fprintf(outFile, " %d %d %d %d",
@@ -2641,7 +2641,7 @@ extOutputDevices(def, transList, outFile)
 		devptr = extDevFindParamMatch(devptr, length, width);
 
 		fprintf(outFile, "%s %s",
-			extDevTable[devptr->exts_deviceClass],
+			extDevTable[(unsigned char)devptr->exts_deviceClass],
 			devptr->exts_deviceName);
 
 		fprintf(outFile, " %d %d %d %d",
@@ -2675,7 +2675,7 @@ extOutputDevices(def, transList, outFile)
 	    case DEV_CAPREV:
 	    case DEV_CSUBCKT:
 		fprintf(outFile, "%s %s",
-			extDevTable[devptr->exts_deviceClass],
+			extDevTable[(unsigned char)devptr->exts_deviceClass],
 			devptr->exts_deviceName);
 
 		fprintf(outFile, " %d %d %d %d",
diff --git a/plot/plotRutils.c b/plot/plotRutils.c
index ec0e2485..8b4b22ee 100644
--- a/plot/plotRutils.c
+++ b/plot/plotRutils.c
@@ -710,7 +710,7 @@ PlotTextSize(font, string, area)
     {
 	if ((*string == ' ') || (*string == '\t'))
 	    d = &font->fo_chars['t'];
-	else d = &font->fo_chars[*string];
+	else d = &font->fo_chars[(unsigned char)*string];
 	if (d->nbytes == 0) continue;
 	if (d->up > area->r_ytop)
 	    area->r_ytop = d->up;
@@ -783,7 +783,7 @@ PlotRasterText(raster, clip, font, string, point)
 	 * area of the raster.
 	 */
 
-	d = &font->fo_chars[*string];
+	d = &font->fo_chars[(unsigned char)*string];
 	cBytesPerLine = (d->left + d->right + 7) >> 3;
 	for (i = 0; i < d->up + d->down; i++)
 	{
diff --git a/resis/ResPrint.c b/resis/ResPrint.c
index 49e8c537..50397eca 100644
--- a/resis/ResPrint.c
+++ b/resis/ResPrint.c
@@ -140,7 +140,7 @@ ResPrintExtDev(outextfile, devices)
 		    fprintf(outextfile,"device ");
 
 		fprintf(outextfile,"%s %s %d %d %d %d ",
-			extDevTable[devptr->exts_deviceClass],
+			extDevTable[(unsigned char)devptr->exts_deviceClass],
 			devptr->exts_deviceName,
 			devices->layout->rd_inside.r_ll.p_x,
 			devices->layout->rd_inside.r_ll.p_y,