diff --git a/Svc/TlmPacketizer/TlmPacketizer.cpp b/Svc/TlmPacketizer/TlmPacketizer.cpp
index 89af22e1d01..ba1c685558c 100644
--- a/Svc/TlmPacketizer/TlmPacketizer.cpp
+++ b/Svc/TlmPacketizer/TlmPacketizer.cpp
@@ -89,10 +89,10 @@ void TlmPacketizer::setPacketList(const TlmPacketizerPacketList& packetList,
             entry.ignored = false;
             entry.channelSize = packetList.list[pktEntry]->list[tlmEntry].size;
             // the offset into the buffer will be the current packet length
-            // the offset must fit within FwSignedSizeType to allow for negative values
-            FW_ASSERT(packetLen <= static_cast<FwSizeType>(std::numeric_limits<FwSignedSizeType>::max()),
+            // the offset must fit within I16 to allow for the -1 sentinel value
+            FW_ASSERT(packetLen <= static_cast<FwSizeType>(std::numeric_limits<I16>::max()),
                       static_cast<FwAssertArgType>(packetLen));
-            entry.packetOffset[pktEntry] = static_cast<FwSignedSizeType>(packetLen);
+            entry.packetOffset[pktEntry] = static_cast<I16>(packetLen);
 
             packetLen += entry.channelSize;
 
diff --git a/Svc/TlmPacketizer/TlmPacketizer.hpp b/Svc/TlmPacketizer/TlmPacketizer.hpp
index 7f80d76d265..ffb58fc5d17 100644
--- a/Svc/TlmPacketizer/TlmPacketizer.hpp
+++ b/Svc/TlmPacketizer/TlmPacketizer.hpp
@@ -172,7 +172,7 @@ class TlmPacketizer final : public TlmPacketizerComponentBase, public Fw::ParamE
         FwChanIdType id;  //!< telemetry id stored in slot
         // Offsets into packet buffers.
         // -1 means that channel is not in that packet
-        FwSignedSizeType packetOffset[MAX_PACKETIZER_PACKETS];
+        I16 packetOffset[MAX_PACKETIZER_PACKETS];
         FwSizeType channelSize;  //!< max serialized size of the channel in bytes
         bool ignored;            //!< ignored channel id
         bool hasValue;           //!< if the entry has received a value at least once