diff --git a/libs/libc/netdb/lib_gethostentbynamer.c b/libs/libc/netdb/lib_gethostentbynamer.c
index ab179f98023..8222ae830a1 100644
--- a/libs/libc/netdb/lib_gethostentbynamer.c
+++ b/libs/libc/netdb/lib_gethostentbynamer.c
@@ -89,7 +89,7 @@ static int lib_numeric_address(FAR const char *name,
   FAR struct hostent_info_s *info;
   FAR char *ptr;
   socklen_t addrlen;
-  int namelen;
+  size_t namelen;
   int ret;
 
   /* Verify that we have a buffer big enough to get started (it still may not
@@ -320,7 +320,7 @@ static int lib_find_answer(FAR const char *name, FAR struct hostent_s *host,
   socklen_t addrlen;
   int naddr;
   int addrtype;
-  int namelen;
+  size_t namelen;
   int ret;
   int i;
 
@@ -466,7 +466,7 @@ static int lib_dns_lookup(FAR const char *name, FAR struct hostent_s *host,
   socklen_t addrlen;
   int naddr;
   int addrtype;
-  int namelen;
+  size_t namelen;
   int ret;
   int i;
 
diff --git a/mm/mempool/mempool_multiple.c b/mm/mempool/mempool_multiple.c
index a71868c6c7b..62e2ecdea65 100644
--- a/mm/mempool/mempool_multiple.c
+++ b/mm/mempool/mempool_multiple.c
@@ -91,7 +91,7 @@ mempool_multiple_find(FAR struct mempool_multiple_s *mpool, size_t size)
 int mempool_multiple_init(FAR struct mempool_multiple_s *mpool,
                           FAR const char *name)
 {
-  int i;
+  size_t i;
 
   DEBUGASSERT(mpool != NULL && mpool->pools != NULL);
 
@@ -359,7 +359,7 @@ void mempool_multiple_fixed_free(FAR struct mempool_multiple_s *mpool,
 
 int mempool_multiple_deinit(FAR struct mempool_multiple_s *mpool)
 {
-  int i;
+  size_t i;
 
   DEBUGASSERT(mpool != NULL);
 
diff --git a/mm/mm_heap/mm_mallinfo.c b/mm/mm_heap/mm_mallinfo.c
index 6f34af838d6..d9275771e08 100644
--- a/mm/mm_heap/mm_mallinfo.c
+++ b/mm/mm_heap/mm_mallinfo.c
@@ -68,7 +68,7 @@ static void mallinfo_handler(FAR struct mm_allocnode_s *node, FAR void *arg)
 
       info->ordblks++;
       info->fordblks += node->size;
-      if (node->size > info->mxordblk)
+      if (node->size > (size_t)info->mxordblk)
         {
           info->mxordblk = node->size;
         }
@@ -123,7 +123,7 @@ int mm_mallinfo(FAR struct mm_heap_s *heap, FAR struct mallinfo *info)
   info->arena = heap->mm_heapsize;
   info->uordblks += region * SIZEOF_MM_ALLOCNODE; /* account for the tail node */
 
-  DEBUGASSERT(info->uordblks + info->fordblks == heap->mm_heapsize);
+  DEBUGASSERT((size_t)info->uordblks + info->fordblks == heap->mm_heapsize);
 
   return OK;
 }