diff --git a/src/ops.c b/src/ops.c
index cfa0bb3..83c36bd 100644
--- a/src/ops.c
+++ b/src/ops.c
@@ -183,8 +183,15 @@
     if (char1 == 'g' && char2 == Ctrl_X)	/* subtract */
 	return OP_NR_SUB;
     for (i = 0; ; ++i)
+    {
 	if (opchars[i][0] == char1 && opchars[i][1] == char2)
 	    break;
+	if (i == (int)(sizeof(opchars) / sizeof(char [3]) - 1))
+	{
+	    internal_error("get_op_type()");
+	    break;
+	}
+    }
     return i;
 }