diff --git a/src/avif.c b/src/avif.c
index 25f4111..0597aa1 100644
--- a/src/avif.c
+++ b/src/avif.c
@@ -722,6 +722,51 @@
 }
 
 // ---------------------------------------------------------------------------
+
+avifBool avifAreGridDimensionsValid(avifPixelFormat yuvFormat, uint32_t imageW, uint32_t imageH, uint32_t tileW, uint32_t tileH, avifDiagnostics * diag)
+{
+    // ISO/IEC 23000-22:2019, Section 7.3.11.4.2:
+    //   - the tile_width shall be greater than or equal to 64, and should be a multiple of 64
+    //   - the tile_height shall be greater than or equal to 64, and should be a multiple of 64
+    // The "should" part is ignored here.
+    if ((tileW < 64) || (tileH < 64)) {
+        avifDiagnosticsPrintf(diag,
+                              "Grid image tile width (%u) or height (%u) cannot be smaller than 64. "
+                              "See MIAF (ISO/IEC 23000-22:2019), Section 7.3.11.4.2",
+                              tileW,
+                              tileH);
+        return AVIF_FALSE;
+    }
+
+    // ISO/IEC 23000-22:2019, Section 7.3.11.4.2:
+    //   - when the images are in the 4:2:2 chroma sampling format the horizontal tile offsets and widths,
+    //     and the output width, shall be even numbers;
+    //   - when the images are in the 4:2:0 chroma sampling format both the horizontal and vertical tile
+    //     offsets and widths, and the output width and height, shall be even numbers.
+    // If the rules above were not respected, the following problematic situation may happen:
+    //   Some 4:2:0 image is 650 pixels wide and has 10 cell columns, each being 65 pixels wide.
+    //   The chroma plane of the whole image is 325 pixels wide. The chroma plane of each cell is 33 pixels wide.
+    //   33*10 - 325 gives 5 extra pixels with no specified destination in the reconstructed image.
+
+    // Tile offsets are not enforced since they depend on tile size (ISO/IEC 23008-12:2017, Section 6.6.2.3.1):
+    //   The reconstructed image is formed by tiling the input images into a grid [...] without gap or overlap
+    if ((((yuvFormat == AVIF_PIXEL_FORMAT_YUV420) || (yuvFormat == AVIF_PIXEL_FORMAT_YUV422)) &&
+         (((imageW % 2) != 0) || ((tileW % 2) != 0))) ||
+        ((yuvFormat == AVIF_PIXEL_FORMAT_YUV420) && (((imageH % 2) != 0) || ((tileH % 2) != 0)))) {
+        avifDiagnosticsPrintf(diag,
+                              "Grid image width (%u) or height (%u) or tile width (%u) or height (%u) "
+                              "shall be even if chroma is subsampled in that dimension. "
+                              "See MIAF (ISO/IEC 23000-22:2019), Section 7.3.11.4.2",
+                              imageW,
+                              imageH,
+                              tileW,
+                              tileH);
+        return AVIF_FALSE;
+    }
+    return AVIF_TRUE;
+}
+
+// ---------------------------------------------------------------------------
 // avifCodecSpecificOption
 
 static char * avifStrdup(const char * str)
diff --git a/src/read.c b/src/read.c
index 3ca86a5..09b4852 100644
--- a/src/read.c
+++ b/src/read.c
@@ -1295,37 +1295,17 @@
                               "Grid image tiles in the rightmost column and bottommost row do not overlap the reconstructed image grid canvas. See MIAF (ISO/IEC 23000-22:2019), Section 7.3.11.4.2, Figure 2");
         return AVIF_FALSE;
     }
-    // Check the restrictions in MIAF (ISO/IEC 23000-22:2019), Section 7.3.11.4.2.
-    //
-    // The tile_width shall be greater than or equal to 64, and the tile_height shall be greater than or equal to 64.
-    if ((firstTile->image->width < 64) || (firstTile->image->height < 64)) {
-        avifDiagnosticsPrintf(data->diag,
-                              "Grid image tiles are smaller than 64x64 (%ux%u). See MIAF (ISO/IEC 23000-22:2019), Section 7.3.11.4.2",
-                              firstTile->image->width,
-                              firstTile->image->height);
-        return AVIF_FALSE;
+
+    if (alpha) {
+        assert(firstTile->image->yuvFormat == AVIF_PIXEL_FORMAT_YUV400);
     }
-    if (!alpha) {
-        if ((firstTile->image->yuvFormat == AVIF_PIXEL_FORMAT_YUV422) || (firstTile->image->yuvFormat == AVIF_PIXEL_FORMAT_YUV420)) {
-            // The horizontal tile offsets and widths, and the output width, shall be even numbers.
-            if (((firstTile->image->width & 1) != 0) || ((grid->outputWidth & 1) != 0)) {
-                avifDiagnosticsPrintf(data->diag,
-                                      "Grid image horizontal tile offsets and widths [%u], and the output width [%u], shall be even numbers.",
-                                      firstTile->image->width,
-                                      grid->outputWidth);
-                return AVIF_FALSE;
-            }
-        }
-        if (firstTile->image->yuvFormat == AVIF_PIXEL_FORMAT_YUV420) {
-            // The vertical tile offsets and heights, and the output height, shall be even numbers.
-            if (((firstTile->image->height & 1) != 0) || ((grid->outputHeight & 1) != 0)) {
-                avifDiagnosticsPrintf(data->diag,
-                                      "Grid image vertical tile offsets and heights [%u], and the output height [%u], shall be even numbers.",
-                                      firstTile->image->height,
-                                      grid->outputHeight);
-                return AVIF_FALSE;
-            }
-        }
+    if (!avifAreGridDimensionsValid(firstTile->image->yuvFormat,
+                                    grid->outputWidth,
+                                    grid->outputHeight,
+                                    firstTile->image->width,
+                                    firstTile->image->height,
+                                    data->diag)) {
+        return AVIF_FALSE;
     }
 
     // Lazily populate dstImage with the new frame's properties. If we're decoding alpha,
diff --git a/src/write.c b/src/write.c
index 657bfaa..cd0a274 100644
--- a/src/write.c
+++ b/src/write.c
@@ -567,15 +567,28 @@
         return AVIF_RESULT_NO_CONTENT;
     }
 
-    if ((cellCount > 1) && ((firstCell->width < 64) || (firstCell->height < 64))) {
+    if ((cellCount > 1) && !avifAreGridDimensionsValid(firstCell->yuvFormat,
+                                                       gridCols * firstCell->width,
+                                                       gridRows * firstCell->height,
+                                                       firstCell->width,
+                                                       firstCell->height,
+                                                       &encoder->diag)) {
         return AVIF_RESULT_INVALID_IMAGE_GRID;
     }
 
     for (uint32_t cellIndex = 0; cellIndex < cellCount; ++cellIndex) {
         const avifImage * cellImage = cellImages[cellIndex];
-        if ((cellImage->depth != firstCell->depth) || (cellImage->width != firstCell->width) ||
-            (cellImage->height != firstCell->height) || (!!cellImage->alphaPlane != !!firstCell->alphaPlane) ||
-            (cellImage->alphaPremultiplied != firstCell->alphaPremultiplied)) {
+        // HEIF (ISO 23008-12:2017), Section 6.6.2.3.1:
+        //   All input images shall have exactly the same width and height; call those tile_width and tile_height.
+        // MIAF (ISO 23000-22:2019), Section 7.3.11.4.1:
+        //   All input images of a grid image item shall use the same coding format, chroma sampling format, and the
+        //   same decoder configuration (see 7.3.6.2).
+        if ((cellImage->width != firstCell->width) || (cellImage->height != firstCell->height) ||
+            (cellImage->depth != firstCell->depth) || (cellImage->yuvFormat != firstCell->yuvFormat) ||
+            (cellImage->yuvRange != firstCell->yuvRange) || (cellImage->colorPrimaries != firstCell->colorPrimaries) ||
+            (cellImage->transferCharacteristics != firstCell->transferCharacteristics) ||
+            (cellImage->matrixCoefficients != firstCell->matrixCoefficients) || (cellImage->alphaRange != firstCell->alphaRange) ||
+            (!!cellImage->alphaPlane != !!firstCell->alphaPlane) || (cellImage->alphaPremultiplied != firstCell->alphaPremultiplied)) {
             return AVIF_RESULT_INVALID_IMAGE_GRID;
         }