diff --git a/modules/basis_universal/image_compress_basisu.cpp b/modules/basis_universal/image_compress_basisu.cpp
index 72e7977eefb..531b738041b 100644
--- a/modules/basis_universal/image_compress_basisu.cpp
+++ b/modules/basis_universal/image_compress_basisu.cpp
@@ -96,17 +96,74 @@ Vector<uint8_t> basis_universal_packer(const Ref<Image> &p_image, Image::UsedCha
 		} break;
 	}
 
+	// Copy the source image data with mipmaps into BasisU.
 	{
-		// Encode the image with mipmaps.
+		const int orig_width = image->get_width();
+		const int orig_height = image->get_height();
+
+		bool is_res_div_4 = (orig_width % 4 == 0) && (orig_height % 4 == 0);
+
+		// Image's resolution rounded up to the nearest values divisible by 4.
+		int next_width = orig_width <= 2 ? orig_width : (orig_width + 3) & ~3;
+		int next_height = orig_height <= 2 ? orig_height : (orig_height + 3) & ~3;
+
 		Vector<uint8_t> image_data = image->get_data();
 		basisu::vector<basisu::image> basisu_mipmaps;
 
+		// Buffer for storing padded mipmap data.
+		Vector<uint32_t> mip_data_padded;
+
 		for (int32_t i = 0; i <= image->get_mipmap_count(); i++) {
 			int ofs, size, width, height;
 			image->get_mipmap_offset_size_and_dimensions(i, ofs, size, width, height);
 
+			const uint8_t *image_mip_data = image_data.ptr() + ofs;
+
+			// Pad the mipmap's data if its resolution isn't divisible by 4.
+			if (image->has_mipmaps() && !is_res_div_4 && (width > 2 && height > 2) && (width != next_width || height != next_height)) {
+				// Source mip's data interpreted as 32-bit RGBA blocks to help with copying pixel data.
+				const uint32_t *mip_src_data = reinterpret_cast<const uint32_t *>(image_mip_data);
+
+				// Reserve space in the padded buffer.
+				mip_data_padded.resize(next_width * next_height);
+				uint32_t *data_padded_ptr = mip_data_padded.ptrw();
+
+				// Pad mipmap to the nearest block by smearing.
+				int x = 0, y = 0;
+				for (y = 0; y < height; y++) {
+					for (x = 0; x < width; x++) {
+						data_padded_ptr[next_width * y + x] = mip_src_data[width * y + x];
+					}
+
+					// First, smear in x.
+					for (; x < next_width; x++) {
+						data_padded_ptr[next_width * y + x] = data_padded_ptr[next_width * y + x - 1];
+					}
+				}
+
+				// Then, smear in y.
+				for (; y < next_height; y++) {
+					for (x = 0; x < next_width; x++) {
+						data_padded_ptr[next_width * y + x] = data_padded_ptr[next_width * y + x - next_width];
+					}
+				}
+
+				// Override the image_mip_data pointer with our temporary Vector.
+				image_mip_data = reinterpret_cast<const uint8_t *>(mip_data_padded.ptr());
+
+				// Override the mipmap's properties.
+				width = next_width;
+				height = next_height;
+				size = mip_data_padded.size() * 4;
+			}
+
+			// Get the next mipmap's resolution.
+			next_width /= 2;
+			next_height /= 2;
+
+			// Copy the source mipmap's data to a BasisU image.
 			basisu::image basisu_image(width, height);
-			memcpy(basisu_image.get_ptr(), image_data.ptr() + ofs, size);
+			memcpy(basisu_image.get_ptr(), image_mip_data, size);
 
 			if (i == 0) {
 				params.m_source_images.push_back(basisu_image);
@@ -132,10 +189,10 @@ Vector<uint8_t> basis_universal_packer(const Ref<Image> &p_image, Image::UsedCha
 
 	// Copy the encoded data to the buffer.
 	{
-		uint8_t *w = basisu_data.ptrw();
-		*(uint32_t *)w = decompress_format;
+		uint8_t *wb = basisu_data.ptrw();
+		*(uint32_t *)wb = decompress_format;
 
-		memcpy(w + 4, basisu_out.get_ptr(), basisu_out.size());
+		memcpy(wb + 4, basisu_out.get_ptr(), basisu_out.size());
 	}
 
 	return basisu_data;
@@ -238,8 +295,7 @@ Ref<Image> basis_universal_unpacker_ptr(const uint8_t *p_data, int p_size) {
 	uint8_t *dst = out_data.ptrw();
 	memset(dst, 0, out_data.size());
 
-	uint32_t mip_count = Image::get_image_required_mipmaps(basisu_info.m_orig_width, basisu_info.m_orig_height, image_format);
-	for (uint32_t i = 0; i <= mip_count; i++) {
+	for (uint32_t i = 0; i < basisu_info.m_total_levels; i++) {
 		basist::basisu_image_level_info basisu_level;
 		transcoder.get_image_level_info(src_ptr, src_size, basisu_level, 0, i);