diff --git a/flang/runtime/allocatable.cpp b/flang/runtime/allocatable.cpp
--- a/flang/runtime/allocatable.cpp
+++ b/flang/runtime/allocatable.cpp
@@ -151,8 +151,15 @@
       descriptor, hasStat, errMsg, sourceFile, sourceLine)};
   if (stat == StatOk) {
     DescriptorAddendum *addendum{descriptor.Addendum()};
-    INTERNAL_CHECK(addendum != nullptr);
-    addendum->set_derivedType(derivedType);
+    if (addendum) { // Unlimited polymorphic allocated from intrinsic type spec
+                    // does not have
+      addendum->set_derivedType(derivedType);
+    } else {
+      // Unlimited polymorphic descriptors initialized with
+      // AllocatableInitIntrinsic do not have an addendum. Make sure the
+      // derivedType is null in that case.
+      INTERNAL_CHECK(!derivedType);
+    }
   }
   return stat;
 }
diff --git a/flang/runtime/pointer.cpp b/flang/runtime/pointer.cpp
--- a/flang/runtime/pointer.cpp
+++ b/flang/runtime/pointer.cpp
@@ -168,8 +168,14 @@
       pointer, hasStat, errMsg, sourceFile, sourceLine)};
   if (stat == StatOk) {
     DescriptorAddendum *addendum{pointer.Addendum()};
-    INTERNAL_CHECK(addendum != nullptr);
-    addendum->set_derivedType(derivedType);
+    if (addendum) {
+      addendum->set_derivedType(derivedType);
+    } else {
+      // Unlimited polymorphic descriptors initialized with
+      // PointerNullifyIntrinsic do not have an addendum. Make sure the
+      // derivedType is null in that case.
+      INTERNAL_CHECK(!derivedType);
+    }
   }
   return stat;
 }
diff --git a/flang/unittests/Runtime/Pointer.cpp b/flang/unittests/Runtime/Pointer.cpp
--- a/flang/unittests/Runtime/Pointer.cpp
+++ b/flang/unittests/Runtime/Pointer.cpp
@@ -51,3 +51,15 @@
   EXPECT_EQ(p->ElementBytes(), m->ElementBytes());
   EXPECT_EQ(p->type(), m->type());
 }
+
+TEST(Pointer, DeallocatePolymorphic) {
+  // CLASS(*) :: p
+  // ALLOCATE(integer::p)
+  auto p{Descriptor::Create(TypeCode{Fortran::common::TypeCategory::Integer, 4},
+      4, nullptr, 0, nullptr, CFI_attribute_pointer)};
+  RTNAME(PointerAllocate)
+  (*p, /*hasStat=*/false, /*errMsg=*/nullptr, __FILE__, __LINE__);
+  // DEALLOCATE(p)
+  RTNAME(PointerDeallocatePolymorphic)
+  (*p, nullptr, /*hasStat=*/false, /*errMsg=*/nullptr, __FILE__, __LINE__);
+}