diff --git a/src/xwinman.c b/src/xwinman.c
index 1eb2379..6f2a0f0 100644
--- a/src/xwinman.c
+++ b/src/xwinman.c
@@ -45,9 +45,16 @@ extern int KBDEventFlg;
 extern u_char *SUNLispKeyMap;
 #define KEYCODE_OFFSET 7 /* Sun Keycode offset */
 
+/* bits within the EmRealUtilin word */
+#define KEYSET_LEFT 8
+#define KEYSET_LEFTMIDDLE 9
+#define KEYSET_MIDDLE  10
+#define KEYSET_RIGHTMIDDLE 11
+#define KEYSET_RIGHT 12
+/* Mouse buttons */
 #define MOUSE_LEFT 13
-#define MOUSE_MIDDLE 15
 #define MOUSE_RIGHT 14
+#define MOUSE_MIDDLE 15
 
 /* bound: return b if it is between a and c otherwise it returns a or c */
 int bound(int a, int b, int c)
@@ -209,6 +216,16 @@ void getXsignaldata(DspInterface dsp)
             case Button1: PUTBASEBIT68K(EmRealUtilin68K, MOUSE_LEFT, FALSE); break;
             case Button2: PUTBASEBIT68K(EmRealUtilin68K, MOUSE_MIDDLE, FALSE); break;
             case Button3: PUTBASEBIT68K(EmRealUtilin68K, MOUSE_RIGHT, FALSE); break;
+            case Button4: PUTBASEBIT68K(EmRealUtilin68K, KEYSET_LEFT, FALSE); break;
+            case Button5: PUTBASEBIT68K(EmRealUtilin68K, KEYSET_LEFTMIDDLE, FALSE); break;
+#if 0
+            /* Button6 and Button7 are not defined, but these values are generated by
+               macOS for the left and right scrolling movements.
+               Leave them out for now, until we've sorted out the up and down scrolling.
+             */
+            case Button5 + 1: PUTBASEBIT68K(EmRealUtilin68K, KEYSET_RIGHTMIDDLE, FALSE); break;
+            case Button5 + 2: PUTBASEBIT68K(EmRealUtilin68K, KEYSET_RIGHT, FALSE); break;
+#endif
             default: break;
           }
           DoRing();
@@ -219,6 +236,13 @@ void getXsignaldata(DspInterface dsp)
             case Button1: PUTBASEBIT68K(EmRealUtilin68K, MOUSE_LEFT, TRUE); break;
             case Button2: PUTBASEBIT68K(EmRealUtilin68K, MOUSE_MIDDLE, TRUE); break;
             case Button3: PUTBASEBIT68K(EmRealUtilin68K, MOUSE_RIGHT, TRUE); break;
+            case Button4: PUTBASEBIT68K(EmRealUtilin68K, KEYSET_LEFT, TRUE); break;
+            case Button5: PUTBASEBIT68K(EmRealUtilin68K, KEYSET_LEFTMIDDLE, TRUE); break;
+#if 0
+            /* See above for key press */
+            case Button5 + 1: PUTBASEBIT68K(EmRealUtilin68K, KEYSET_RIGHTMIDDLE, TRUE); break;
+            case Button5 + 2: PUTBASEBIT68K(EmRealUtilin68K, KEYSET_RIGHT, TRUE); break;
+#endif
             default: break;
           }
           DoRing();