diff --git a/allchblk.c b/allchblk.c
index 8cb6e4792..5d2b1e7d8 100644
--- a/allchblk.c
+++ b/allchblk.c
@@ -187,7 +187,7 @@ STATIC int GC_hblk_fl_from_blocks(size_t blocks_needed)
 
   GC_API void GC_CALL GC_dump_regions(void)
   {
-    unsigned i;
+    size_t i;
 
     for (i = 0; i < GC_n_heap_sects; ++i) {
         ptr_t start = GC_heap_sects[i].hs_start;
diff --git a/alloc.c b/alloc.c
index e3519c139..4a3093f6a 100644
--- a/alloc.c
+++ b/alloc.c
@@ -1403,7 +1403,7 @@ STATIC void GC_add_to_heap(struct hblk *h, size_t sz)
     size_t old_capacity = 0;
     void *old_heap_sects = NULL;
 #   ifdef GC_ASSERTIONS
-      unsigned i;
+      size_t i;
 #   endif
 
     GC_ASSERT(I_HOLD_LOCK());
@@ -1417,14 +1417,14 @@ STATIC void GC_add_to_heap(struct hblk *h, size_t sz)
 #     ifndef INITIAL_HEAP_SECTS
 #       define INITIAL_HEAP_SECTS 32
 #     endif
-      size_t new_capacity = GC_n_heap_sects > 0 ?
-                (size_t)GC_n_heap_sects * 2 : INITIAL_HEAP_SECTS;
+      size_t new_capacity = GC_n_heap_sects > 0
+                                ? GC_n_heap_sects * 2 : INITIAL_HEAP_SECTS;
       void *new_heap_sects =
                 GC_scratch_alloc(new_capacity * sizeof(struct HeapSect));
 
       if (NULL == new_heap_sects) {
         /* Retry with smaller yet sufficient capacity.  */
-        new_capacity = (size_t)GC_n_heap_sects + INITIAL_HEAP_SECTS;
+        new_capacity = GC_n_heap_sects + INITIAL_HEAP_SECTS;
         new_heap_sects =
                 GC_scratch_alloc(new_capacity * sizeof(struct HeapSect));
         if (NULL == new_heap_sects)
@@ -1521,7 +1521,7 @@ STATIC void GC_add_to_heap(struct hblk *h, size_t sz)
 #if !defined(NO_DEBUGGING)
   void GC_print_heap_sects(void)
   {
-    unsigned i;
+    size_t i;
 
     GC_printf("Total heap size: %lu" IF_USE_MUNMAP(" (%lu unmapped)") "\n",
               (unsigned long)GC_heapsize /*, */
diff --git a/blacklst.c b/blacklst.c
index df1271988..73f001fd2 100644
--- a/blacklst.c
+++ b/blacklst.c
@@ -290,7 +290,7 @@ STATIC word GC_number_stack_black_listed(struct hblk *start,
 /* Return the total number of (stack) black-listed bytes. */
 static word total_stack_black_listed(void)
 {
-    unsigned i;
+    size_t i;
     word total = 0;
 
     for (i = 0; i < GC_n_heap_sects; i++) {
diff --git a/checksums.c b/checksums.c
index 9c728fc15..0c130a9eb 100644
--- a/checksums.c
+++ b/checksums.c
@@ -58,7 +58,7 @@ STATIC GC_bool GC_was_faulted(struct hblk *h)
 STATIC word GC_checksum(struct hblk *h)
 {
     word *p;
-    word *lim = (word *)(h+1);
+    word *lim = (word *)(h + 1);
     word result = 0;
 
     for (p = (word *)h; ADDR_LT((ptr_t)p, (ptr_t)lim); p++) {
@@ -138,7 +138,7 @@ STATIC void GC_check_blocks(void)
 void GC_check_dirty(void)
 {
     int index;
-    unsigned i;
+    size_t i;
 
     GC_check_blocks();
     GC_n_dirty_errors = 0;
diff --git a/extra/MacOS.c b/extra/MacOS.c
index a2a978a64..87a68a437 100644
--- a/extra/MacOS.c
+++ b/extra/MacOS.c
@@ -100,7 +100,7 @@ Ptr GC_MacTemporaryNewPtr(size_t size, Boolean clearMemory)
 static void perform_final_collection(void)
 {
   unsigned i;
-  word last_fo_entries = 0;
+  size_t last_fo_entries = 0;
 
   /* adjust the stack bottom, because CFM calls us from another stack
      location. */
diff --git a/include/private/gc_priv.h b/include/private/gc_priv.h
index 606652d98..9855305ff 100644
--- a/include/private/gc_priv.h
+++ b/include/private/gc_priv.h
@@ -1533,7 +1533,7 @@ struct _GC_arrays {
 # define GC_capacity_heap_sects GC_arrays._capacity_heap_sects
   size_t _capacity_heap_sects;
 # define GC_n_heap_sects GC_arrays._n_heap_sects
-  word _n_heap_sects;   /* Number of separately added heap sections.    */
+  size_t _n_heap_sects; /* number of separately added heap sections */
 # ifdef ANY_MSWIN
 #   define GC_n_heap_bases GC_arrays._n_heap_bases
     size_t _n_heap_bases; /* see GC_heap_bases[] */
@@ -1547,7 +1547,7 @@ struct _GC_arrays {
     ptr_t *_gcjobjfreelist;
 # endif
 # define GC_fo_entries GC_arrays._fo_entries
-  word _fo_entries;
+  size_t _fo_entries;
 # ifndef GC_NO_FINALIZATION
 #   define GC_dl_hashtbl GC_arrays._dl_hashtbl
 #   define GC_fnlz_roots GC_arrays._fnlz_roots