diff --git a/rmw_fastrtps_cpp/src/type_support_common.cpp b/rmw_fastrtps_cpp/src/type_support_common.cpp
index 6e92d52e5a..25d0d1b661 100644
--- a/rmw_fastrtps_cpp/src/type_support_common.cpp
+++ b/rmw_fastrtps_cpp/src/type_support_common.cpp
@@ -75,7 +75,7 @@ void TypeSupport::set_members(const message_type_support_callbacks_t * members)
 
     key_max_serialized_size_ = key_callbacks_->max_serialized_size_key(key_is_unbounded_);
     if (!key_is_unbounded_) {
-      key_buffer_.reserve(key_max_serialized_size_);
+      key_buffer_.resize(key_max_serialized_size_);
     }
   }
 }
@@ -165,7 +165,7 @@ bool TypeSupport::get_key_hash_from_ros_message(
     key_max_serialized_size_ = (std::max) (
       key_max_serialized_size_,
       key_callbacks_->get_serialized_size_key(ros_message));
-    key_buffer_.reserve(key_max_serialized_size_);
+    key_buffer_.resize(key_max_serialized_size_);
   }
 
   eprosima::fastcdr::FastBuffer fast_buffer(
@@ -179,7 +179,7 @@ bool TypeSupport::get_key_hash_from_ros_message(
 
   const size_t max_serialized_key_length = 16;
 
-  auto ser_length = ser.get_serialized_data_length();
+  const auto ser_length = ser.get_serialized_data_length();
 
   // check for md5
   if (force_md5 || key_max_serialized_size_ > max_serialized_key_length) {
diff --git a/rmw_fastrtps_dynamic_cpp/src/MessageTypeSupport_impl.hpp b/rmw_fastrtps_dynamic_cpp/src/MessageTypeSupport_impl.hpp
index 84405be569..0be8a22241 100644
--- a/rmw_fastrtps_dynamic_cpp/src/MessageTypeSupport_impl.hpp
+++ b/rmw_fastrtps_dynamic_cpp/src/MessageTypeSupport_impl.hpp
@@ -65,7 +65,7 @@ MessageTypeSupport<MembersType>::MessageTypeSupport(
   if (this->members_->has_any_key_member_) {
     this->key_max_serialized_size_ = this->calculateMaxSerializedKeySize(members);
     this->is_compute_key_provided = true;
-    this->key_buffer_.reserve(this->key_max_serialized_size_);
+    this->key_buffer_.resize(this->key_max_serialized_size_);
   }
 
   // Account for RTPS submessage alignment
diff --git a/rmw_fastrtps_dynamic_cpp/src/ServiceTypeSupport_impl.hpp b/rmw_fastrtps_dynamic_cpp/src/ServiceTypeSupport_impl.hpp
index bed1661af5..7110430edd 100644
--- a/rmw_fastrtps_dynamic_cpp/src/ServiceTypeSupport_impl.hpp
+++ b/rmw_fastrtps_dynamic_cpp/src/ServiceTypeSupport_impl.hpp
@@ -66,7 +66,7 @@ RequestTypeSupport<ServiceMembersType, MessageMembersType>::RequestTypeSupport(
   if (this->members_->has_any_key_member_) {
     this->key_max_serialized_size_ = this->calculateMaxSerializedKeySize(this->members_);
     this->is_compute_key_provided = true;
-    this->key_buffer_.reserve(this->key_max_serialized_size_);
+    this->key_buffer_.resize(this->key_max_serialized_size_);
   }
 
   // Account for RTPS submessage alignment
@@ -109,7 +109,7 @@ ResponseTypeSupport<ServiceMembersType, MessageMembersType>::ResponseTypeSupport
   if (this->members_->has_any_key_member_) {
     this->key_max_serialized_size_ = this->calculateMaxSerializedKeySize(this->members_);
     this->is_compute_key_provided = true;
-    this->key_buffer_.reserve(this->key_max_serialized_size_);
+    this->key_buffer_.resize(this->key_max_serialized_size_);
   }
 
   // Account for RTPS submessage alignment
diff --git a/rmw_fastrtps_dynamic_cpp/src/TypeSupport_impl.hpp b/rmw_fastrtps_dynamic_cpp/src/TypeSupport_impl.hpp
index 06c35c4bf4..68c33dd142 100644
--- a/rmw_fastrtps_dynamic_cpp/src/TypeSupport_impl.hpp
+++ b/rmw_fastrtps_dynamic_cpp/src/TypeSupport_impl.hpp
@@ -18,6 +18,7 @@
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
+#include <cstring>
 #include <string>
 #include <vector>
 
@@ -363,7 +364,7 @@ bool TypeSupport<MembersType>::get_key_hash_from_ros_message(
     this->key_max_serialized_size_ =
       (std::max) (this->key_max_serialized_size_,
       this->getEstimatedSerializedKeySize(members, ros_message));
-    key_buffer_.reserve(this->key_max_serialized_size_);
+    key_buffer_.resize(this->key_max_serialized_size_);
   }
 
   eprosima::fastcdr::FastBuffer buffer(
@@ -376,22 +377,24 @@ bool TypeSupport<MembersType>::get_key_hash_from_ros_message(
   // serialize
   serializeKeyROSmessage(ser, members_, ros_message);
 
-  // check for md5
+  const size_t max_serialized_key_length = 16;
+
+  const auto ser_length = ser.get_serialized_data_length();
+
   if (force_md5 || this->key_max_serialized_size_ > 16) {
     md5_.init();
 
-    md5_.update(
-      this->key_buffer_.data(),
-      static_cast<unsigned int>(ser.get_serialized_data_length()));
+    md5_.update(key_buffer_.data(), static_cast<unsigned int>(ser_length));
 
     md5_.finalize();
 
-    for (uint8_t i = 0; i < 16; ++i) {
+    for (uint8_t i = 0; i < max_serialized_key_length; ++i) {
       ihandle->value[i] = md5_.digest[i];
     }
   } else {
-    for (uint8_t i = 0; i < 16; ++i) {
-      ihandle->value[i] = this->key_buffer_[i];
+    memset(ihandle->value, 0, max_serialized_key_length);
+    for (uint8_t i = 0; i < ser_length; ++i) {
+      ihandle->value[i] = key_buffer_[i];
     }
   }