diff --git a/hw/spapr_hcall.c b/hw/spapr_hcall.c
index 194d9c24b5..762493a0f7 100644
--- a/hw/spapr_hcall.c
+++ b/hw/spapr_hcall.c
@@ -670,11 +670,10 @@ void spapr_register_hypercall(target_ulong opcode, spapr_hcall_fn fn)
     } else {
         assert((opcode >= KVMPPC_HCALL_BASE) && (opcode <= KVMPPC_HCALL_MAX));
 
-
         slot = &kvmppc_hypercall_table[opcode - KVMPPC_HCALL_BASE];
     }
 
-    assert(!(*slot) || (fn == *slot));
+    assert(!(*slot));
     *slot = fn;
 }
 
diff --git a/hw/spapr_rtas.c b/hw/spapr_rtas.c
index 67da27ba51..ce76c5856a 100644
--- a/hw/spapr_rtas.c
+++ b/hw/spapr_rtas.c
@@ -241,6 +241,15 @@ target_ulong spapr_rtas_call(sPAPREnvironment *spapr,
 
 void spapr_rtas_register(const char *name, spapr_rtas_fn fn)
 {
+    int i;
+
+    for (i = 0; i < (rtas_next - rtas_table); i++) {
+        if (strcmp(name, rtas_table[i].name) == 0) {
+            fprintf(stderr, "RTAS call \"%s\" registered twice\n", name);
+            exit(1);
+        }
+    }
+
     assert(rtas_next < (rtas_table + TOKEN_MAX));
 
     rtas_next->name = name;