diff --git a/jumpforth.S b/jumpforth.S
index 9c198f0..3b8b876 100644
--- a/jumpforth.S
+++ b/jumpforth.S
@@ -459,7 +459,7 @@ defcode ABS
 0: push %eax
    NEXT
 
-/* ( n1 n2 -- n1*n2 ) ( ignores overflow ) */
+/* ( n1|u1 n2|u2 -- n3|u3 ) Multiply (signed or unsigned) */
 defcode MUL,"*"
    pop %eax
    pop %ebx
@@ -467,7 +467,7 @@ defcode MUL,"*"
    push %eax
    NEXT
 
-/* ( n1 n2 -- d ) Multiply, producting a double-cell result */
+/* ( n1 n2 -- d ) Multiply signed, producting a double-cell result */
 defcode MMUL,"M*"
    pop %eax
    pop %ebx
@@ -476,14 +476,6 @@ defcode MMUL,"M*"
    push %edx
    NEXT
 
-/* ( u1 u2 -- u1*u2 ) ( ignores overflow ) */
-defcode UMUL,"U*"
-   pop %eax
-   pop %ebx
-   mull %ebx
-   push %eax
-   NEXT
-
 /* ( u1 u2 -- ud ) Multiply unsigned, producting a double-cell result */
 defcode UMMUL,"UM*"
    pop %eax
@@ -516,6 +508,21 @@ defcode DSUB,"D-"
    sbbl %ebx,(%esp)
    NEXT
 
+/* ( d1|ud1 d2|ud2 -- d3|ud3 ) Double-cell multiplication */
+defcode DMUL,"D*"
+   pop %ecx
+   pop %eax
+   pop %ebx
+   pop %edx
+   imul %edx,%ecx
+   imul %eax,%ebx
+   mul %edx
+   add %ebx,%ecx
+   add %ecx,%edx
+   push %eax
+   push %edx
+   NEXT
+
 defcode DNEGATE
    notl 4(%esp)
    notl (%esp)