=== modified file 'driver-csi.c'
--- driver-csi.c	2017-03-29 19:26:44 +0000
+++ driver-csi.c	2012-11-30 16:34:47 +0000
@@ -644,29 +644,23 @@
 
   TermKeyCsi *csi = info;
 
-  switch(CHARAT(0)) {
-    case 0x1b:
-      if(tk->buffcount < 2)
-        return TERMKEY_RES_NONE;
-
-      switch(CHARAT(1)) {
-        case 0x4f: // ESC-prefixed SS3
-          return peekkey_ss3(tk, csi, 2, key, force, nbytep);
-
-        case 0x5b: // ESC-prefixed CSI
-          return peekkey_csi(tk, csi, 2, key, force, nbytep);
-      }
-
-      return TERMKEY_RES_NONE;
-
-    case 0x8f: // SS3
-      return peekkey_ss3(tk, csi, 1, key, force, nbytep);
-
-    case 0x9b: // CSI
-      return peekkey_csi(tk, csi, 1, key, force, nbytep);
-  }
-
-  return TERMKEY_RES_NONE;
+  // Now we're sure at least 1 byte is valid
+  unsigned char b0 = CHARAT(0);
+
+  if(b0 == 0x1b && tk->buffcount > 1 && CHARAT(1) == '[') {
+    return peekkey_csi(tk, csi, 2, key, force, nbytep);
+  }
+  else if(b0 == 0x1b && tk->buffcount > 1 && CHARAT(1) == 'O') {
+    return peekkey_ss3(tk, csi, 2, key, force, nbytep);
+  }
+  else if(b0 == 0x8f) {
+    return peekkey_ss3(tk, csi, 1, key, force, nbytep);
+  }
+  else if(b0 == 0x9b) {
+    return peekkey_csi(tk, csi, 1, key, force, nbytep);
+  }
+  else
+    return TERMKEY_RES_NONE;
 }
 
 struct TermKeyDriver termkey_driver_csi = {