diff --git a/ir/attrs.h b/ir/attrs.h
index 9ba88e959..9457b66b3 100644
--- a/ir/attrs.h
+++ b/ir/attrs.h
@@ -159,6 +159,7 @@ class FnAttrs final {
   void add(AllocKind k) { allockind |= (uint8_t)k; }
   bool has(AllocKind k) const { return allockind & (uint8_t)k; }
   bool isAlloc() const { return allockind != 0 || has(AllocSize); }
+  bool isAllocWithoutSize() const { return allockind != 0 && !has(AllocSize); }
 
   void inferImpliedAttributes();
 
diff --git a/ir/instr.cpp b/ir/instr.cpp
index 3a560a57d..472c5174e 100644
--- a/ir/instr.cpp
+++ b/ir/instr.cpp
@@ -2768,7 +2768,31 @@ StateValue FnCall::toSMT(State &s) const {
   if (attrs.has(AllocKind::Alloc) ||
       attrs.has(AllocKind::Realloc) ||
       attrs.has(FnAttrs::AllocSize)) {
-    auto [size, np_size] = attrs.computeAllocSize(s, args);
+
+    smt::expr size;
+    smt::expr np_size;
+
+    if (!attrs.has(FnAttrs::AllocSize)) {
+      static IntType sizet_type(string("size_t"), config::max_sizet_bits);
+      FnAttrs new_attrs = attrs;
+      new_attrs.mem.setCanOnlyAccess(MemoryAccess::Inaccessible);
+      auto result = s.addFnCall(std::move(fnName_mangled).str(), std::move(inputs),
+                         std::move(ptr_inputs), sizet_type, StateValue{},
+                         nullptr, std::vector<StateValue>{}, new_attrs, indirect_hash);
+      size = std::move(result.value);
+      np_size = std::move(result.non_poison);
+    } else {
+
+      FnAttrs new_attrs = attrs;
+      new_attrs.mem.setCanOnlyAccess(MemoryAccess::Inaccessible);
+      s.addFnCall(std::move(fnName_mangled).str(), std::move(inputs),
+           std::move(ptr_inputs), Type::voidTy, StateValue{},
+           nullptr, std::vector<StateValue>{}, new_attrs, indirect_hash);
+      auto result = attrs.computeAllocSize(s, args);
+      size = std::move(result.first);
+      np_size = std::move(result.second);
+    }
+    
     expr nonnull = attrs.isNonNull() ? expr(true)
                                      : expr::mkBoolVar("malloc_never_fails");
     // FIXME: alloc-family below
diff --git a/tests/alive-tv/attrs/noallocsize-fn.srctgt.ll b/tests/alive-tv/attrs/noallocsize-fn.srctgt.ll
new file mode 100644
index 000000000..967a4f32c
--- /dev/null
+++ b/tests/alive-tv/attrs/noallocsize-fn.srctgt.ll
@@ -0,0 +1,14 @@
+; ERROR: Source and target don't have the same return domain
+
+define i64 @src() {
+  %stack = call ptr @myalloc()
+  %sz = call i64 @llvm.objectsize.i64.p0(ptr %stack, i1 false, i1 false, i1 false)
+  ret i64 %sz
+}
+
+define i64 @tgt() {
+  ret i64 -1
+}
+
+declare ptr @myalloc() allockind("alloc")
+declare i64 @llvm.objectsize.i64.p0(ptr, i1, i1, i1)
diff --git a/tools/transform.cpp b/tools/transform.cpp
index 8f705526d..b6f63cfb2 100644
--- a/tools/transform.cpp
+++ b/tools/transform.cpp
@@ -1162,6 +1162,9 @@ static void calculateAndInitConstants(Transform &t) {
               fn->getGlobalVar(string_view(call->getFnName()).substr(1)) &&
               inaccessiblememonly_fns.emplace(call->getName()).second)
             ++num_inaccessiblememonly_fns;
+        } else {
+          if (inaccessiblememonly_fns.emplace(call->getName()).second)
+            ++num_inaccessiblememonly_fns;
         }
         if (call->isIndirect()) {
           has_indirect_fncalls = true;