diff --git a/src/lib/support/BufferWriter.cpp b/src/lib/support/BufferWriter.cpp
index c606cba6e2b37d..2ba03e22d24e03 100644
--- a/src/lib/support/BufferWriter.cpp
+++ b/src/lib/support/BufferWriter.cpp
@@ -73,8 +73,9 @@ LittleEndian::BufferWriter & LittleEndian::BufferWriter::EndianPutSigned(int64_t
 
 BigEndian::BufferWriter & BigEndian::BufferWriter::EndianPut(uint64_t x, size_t size)
 {
-    while (size-- > 0)
+    while (size > 0)
     {
+        size--;
         Put(static_cast<uint8_t>((x >> (size * 8)) & 0xff));
     }
     return *this;
@@ -82,8 +83,9 @@ BigEndian::BufferWriter & BigEndian::BufferWriter::EndianPut(uint64_t x, size_t
 
 BigEndian::BufferWriter & BigEndian::BufferWriter::EndianPutSigned(int64_t x, size_t size)
 {
-    while (size-- > 0)
+    while (size > 0)
     {
+        size--;
         Put(static_cast<uint8_t>((x >> (size * 8)) & 0xff));
     }
     return *this;
diff --git a/src/lib/support/CHIPMemString.h b/src/lib/support/CHIPMemString.h
index 51341192a76250..3b74acdbcaf195 100644
--- a/src/lib/support/CHIPMemString.h
+++ b/src/lib/support/CHIPMemString.h
@@ -82,12 +82,20 @@ inline void CopyString(char (&dest)[N], const char * source)
  */
 inline void CopyString(char * dest, size_t destLength, ByteSpan source)
 {
-    if (dest && destLength)
+    if ((dest == nullptr) || (destLength == 0))
     {
-        size_t maxChars = std::min(destLength - 1, source.size());
-        memcpy(dest, source.data(), maxChars);
-        dest[maxChars] = '\0';
+        return; // no space to copy anything, not even a null terminator
     }
+
+    if (source.empty())
+    {
+        *dest = '\0'; // just a null terminator, we are copying empty data
+        return;
+    }
+
+    size_t maxChars = std::min(destLength - 1, source.size());
+    memcpy(dest, source.data(), maxChars);
+    dest[maxChars] = '\0';
 }
 
 /**