diff --git a/src/libImaging/Histo.c b/src/libImaging/Histo.c
index 0bfc8dfe9..2b35873e8 100644
--- a/src/libImaging/Histo.c
+++ b/src/libImaging/Histo.c
@@ -41,7 +41,9 @@ ImagingHistogramNew(Imaging im)
 
     /* Create histogram descriptor */
     h = calloc(1, sizeof(struct ImagingHistogramInstance));
-    strncpy(h->mode, im->mode, IMAGING_MODE_LENGTH);
+    strncpy(h->mode, im->mode, IMAGING_MODE_LENGTH-1);
+    h->mode[IMAGING_MODE_LENGTH-1] = 0;
+
     h->bands = im->bands;
     h->histogram = calloc(im->pixelsize, 256 * sizeof(long));
 
diff --git a/src/libImaging/Palette.c b/src/libImaging/Palette.c
index 31c2c0245..7aee6e8ee 100644
--- a/src/libImaging/Palette.c
+++ b/src/libImaging/Palette.c
@@ -37,7 +37,8 @@ ImagingPaletteNew(const char* mode)
     if (!palette)
         return (ImagingPalette) ImagingError_MemoryError();
 
-    strncpy(palette->mode, mode, IMAGING_MODE_LENGTH);
+    strncpy(palette->mode, mode, IMAGING_MODE_LENGTH-1);
+    palette->mode[IMAGING_MODE_LENGTH-1] = 0;
 
     /* Initialize to ramp */
     for (i = 0; i < 256; i++) {