diff --git a/release/amd64/mkisoimages.sh b/release/amd64/mkisoimages.sh
--- a/release/amd64/mkisoimages.sh
+++ b/release/amd64/mkisoimages.sh
@@ -112,7 +112,11 @@
 
 	# Create a GPT image containing the partitions we need for hybrid boot.
 	hybridfilename=$(mktemp /tmp/hybrid.img.XXXXXX)
-	imgsize=`stat -f %z "$NAME"`
+	if [ "$(uname -s)" = "Linux" ]; then
+		imgsize=`stat -c %s "$NAME"`
+	else
+		imgsize=`stat -f %z "$NAME"`
+	fi
 	$MKIMG -s gpt \
 	    --capacity $imgsize \
 	    -b "$BASEBITSDIR/boot/pmbr" \
diff --git a/release/arm64/mkisoimages.sh b/release/arm64/mkisoimages.sh
--- a/release/arm64/mkisoimages.sh
+++ b/release/arm64/mkisoimages.sh
@@ -107,7 +107,11 @@
 
 	# Create a GPT image containing the EFI partition.
 	efifilename=$(mktemp /tmp/efi.img.XXXXXX)
-	imgsize=`stat -f %z "$NAME"`
+	if [ "$(uname -s)" = "Linux" ]; then
+		imgsize=`stat -c %s "$NAME"`
+	else
+		imgsize=`stat -f %z "$NAME"`
+	fi
 	$MKIMG -s gpt \
 	    --capacity $imgsize \
 	    $espparam \
diff --git a/release/riscv/mkisoimages.sh b/release/riscv/mkisoimages.sh
--- a/release/riscv/mkisoimages.sh
+++ b/release/riscv/mkisoimages.sh
@@ -107,7 +107,11 @@
 
 	# Create a GPT image containing the EFI partition.
 	efifilename=$(mktemp /tmp/efi.img.XXXXXX)
-	imgsize=`stat -f %z "$NAME"`
+	if [ "$(uname -s)" = "Linux" ]; then
+		imgsize=`stat -c %s "$NAME"`
+	else
+		imgsize=`stat -f %z "$NAME"`
+	fi
 	$MKIMG -s gpt \
 	    --capacity $imgsize \
 	    $espparam \