diff --git a/script/opcode-check.sh b/script/opcode-check.sh
new file mode 100755
index 0000000..730dbec
--- /dev/null
+++ b/script/opcode-check.sh
@@ -0,0 +1,23 @@
+#!/bin/sh
+
+# Get the full path to this script while handling spaces and symlinks correctly
+scriptPath="$(cd -P -- "$(dirname -- "$0")" && pwd -P)"
+cd "$scriptPath/.." || exit 1
+
+opcode_check() {
+	path="$1"
+	file="$(basename "$path")"
+
+	max=255
+	for i in $(seq 1 "$max")
+	do
+		opcode=$(printf "0x%.2x\n" "$i")
+		# Pattern: case 0x??:
+		if ! grep -q "case $opcode:" "$path"; then
+			echo "missing opcode: $opcode in $file"
+		fi
+	done
+}
+
+opcode_check "src/cpu.cpp"
+opcode_check "src/cpu-prefix.cpp"