diff --git a/libImaging/Filter.c b/libImaging/Filter.c
index 4c8b81587..d34bbfb85 100644
--- a/libImaging/Filter.c
+++ b/libImaging/Filter.c
@@ -31,6 +31,7 @@ ImagingExpand(Imaging imIn, int xmargin, int ymargin, int mode)
 {
     Imaging imOut;
     int x, y;
+    ImagingSectionCookie cookie;
 
     if (xmargin < 0 && ymargin < 0)
         return (Imaging) ImagingError_ValueError("bad kernel size");
@@ -60,11 +61,13 @@ ImagingExpand(Imaging imIn, int xmargin, int ymargin, int mode)
         EXPAND_LINE(type, image, imIn->ysize-1, ymargin+imIn->ysize+y);\
     }
 
+    ImagingSectionEnter(&cookie);
     if (imIn->image8) {
         EXPAND(UINT8, image8);
     } else {
         EXPAND(INT32, image32);
     }
+    ImagingSectionLeave(&cookie);
 
     ImagingCopyInfo(imOut, imIn);
 
@@ -78,6 +81,7 @@ ImagingFilter(Imaging im, int xsize, int ysize, const FLOAT32* kernel,
     Imaging imOut;
     int x, y;
     FLOAT32 sum;
+    ImagingSectionCookie cookie;
 
     if (!im || strcmp(im->mode, "L") != 0)
         return (Imaging) ImagingError_ModeError();
@@ -131,6 +135,7 @@ ImagingFilter(Imaging im, int xsize, int ysize, const FLOAT32* kernel,
     (int) image[y-2][x+d]   * kernel[23] + \
     (int) image[y-2][x+d+d] * kernel[24])
 
+    ImagingSectionEnter(&cookie);
     if (xsize == 3) {
         /* 3x3 kernel. */
         for (x = 0; x < im->xsize; x++)
@@ -174,6 +179,7 @@ ImagingFilter(Imaging im, int xsize, int ysize, const FLOAT32* kernel,
             for (x = 0; x < im->xsize; x++)
                 imOut->image8[y][x] = im->image8[y][x];
     }
+    ImagingSectionLeave(&cookie);
     return imOut;
 }