diff --git a/basis/cpu/x86/32/bootstrap.factor b/basis/cpu/x86/32/bootstrap.factor
index afcae6d4d9..8a5e43da31 100644
--- a/basis/cpu/x86/32/bootstrap.factor
+++ b/basis/cpu/x86/32/bootstrap.factor
@@ -126,12 +126,13 @@ IN: bootstrap.x86
     ! Compute new stack pointer -- 'dst' for memcpy
     EAX EDX SUB
     ! Install new stack pointer
-    RSP EAX MOV
+    ESP EAX MOV
     ! Call memcpy
-    ESP 8 [+] EDX MOV
-    ESP 4 [+] EBP MOV
-    ESP [] EAX MOV
-    0 CALL "memcpy" f rc-relative jit-dlsym
+    EDX PUSH
+    EBP PUSH
+    EAX PUSH
+    0 CALL "factor_memcpy" f rc-relative jit-dlsym
+    ESP 12 ADD
     ! Return with new callstack
     0 RET
 ] \ set-callstack define-sub-primitive
diff --git a/basis/cpu/x86/64/bootstrap.factor b/basis/cpu/x86/64/bootstrap.factor
index 55dba215d7..2d0296e159 100644
--- a/basis/cpu/x86/64/bootstrap.factor
+++ b/basis/cpu/x86/64/bootstrap.factor
@@ -121,8 +121,12 @@ IN: bootstrap.x86
     ! Install new stack pointer
     RSP arg1 MOV
     ! Call memcpy; arguments are now in the correct registers
-    safe-reg 0 MOV "memcpy" f rc-absolute-cell jit-dlsym
+    ! Create register shadow area for Win64
+    RSP 32 SUB
+    safe-reg 0 MOV "factor_memcpy" f rc-absolute-cell jit-dlsym
     safe-reg CALL
+    ! Tear down register shadow area
+    RSP 32 ADD
     ! Return with new callstack
     0 RET
 ] \ set-callstack define-sub-primitive
diff --git a/vm/utilities.cpp b/vm/utilities.cpp
index 8f063a9ad4..3e976d0619 100755
--- a/vm/utilities.cpp
+++ b/vm/utilities.cpp
@@ -18,4 +18,11 @@ cell read_cell_hex()
 	return cell;
 }
 
+/* On Windows, memcpy() is in a different DLL and the non-optimizing
+compiler can't find it */
+VM_C_API void *factor_memcpy(void *dst, void *src, size_t len)
+{
+	return memcpy(dst,src,len);
+}
+
 }