diff --git a/repos/base/include/base/slab.h b/repos/base/include/base/slab.h
index cf6b397771..a8eb1f87eb 100644
--- a/repos/base/include/base/slab.h
+++ b/repos/base/include/base/slab.h
@@ -40,7 +40,7 @@ class Genode::Slab_block
 		enum { FREE, USED };
 
 		Slab    *_slab;    /* back reference to slab allocator */
-		unsigned _avail;   /* free entries of this block       */
+		size_t   _avail;   /* free entries of this block       */
 
 		/*
 		 * Each slab block consists of three areas, a fixed-size header
diff --git a/repos/base/src/base/allocator/slab.cc b/repos/base/src/base/allocator/slab.cc
index c72e3a36cf..57d5d39844 100644
--- a/repos/base/src/base/allocator/slab.cc
+++ b/repos/base/src/base/allocator/slab.cc
@@ -45,7 +45,7 @@ Slab_entry *Slab_block::slab_entry(int idx)
 	 * of 'num_elem' bytes. We align the first slot to a four-aligned
 	 * address.
 	 */
-	return (Slab_entry *)&_data[align_addr(_slab->num_elem(), 2)
+	return (Slab_entry *)&_data[align_addr(_slab->num_elem(), log2(sizeof(addr_t)))
 	                            + _slab->entry_size()*idx];
 }
 
diff --git a/repos/base/src/base/heap/heap.cc b/repos/base/src/base/heap/heap.cc
index 2018c7658c..47da4e66f4 100644
--- a/repos/base/src/base/heap/heap.cc
+++ b/repos/base/src/base/heap/heap.cc
@@ -87,7 +87,7 @@ Heap::Dataspace *Heap::_allocate_dataspace(size_t size, bool enforce_separate_me
 		_alloc.add_range((addr_t)ds_addr, size);
 
 		/* allocate the Dataspace structure */
-		if (_alloc.alloc_aligned(sizeof(Heap::Dataspace), &ds_meta_data_addr, 2).is_error()) {
+		if (_alloc.alloc_aligned(sizeof(Heap::Dataspace), &ds_meta_data_addr, log2(sizeof(addr_t))).is_error()) {
 			PWRN("could not allocate dataspace meta data - this should never happen");
 			return 0;
 		}
@@ -104,7 +104,7 @@ Heap::Dataspace *Heap::_allocate_dataspace(size_t size, bool enforce_separate_me
 
 bool Heap::_try_local_alloc(size_t size, void **out_addr)
 {
-	if (_alloc.alloc_aligned(size, out_addr, 2).is_error())
+	if (_alloc.alloc_aligned(size, out_addr, log2(sizeof(addr_t))).is_error())
 		return false;
 
 	_quota_used += size;