diff --git a/changes/bug18716 b/changes/bug18716
new file mode 100644
index 0000000000..b15a343f4c
--- /dev/null
+++ b/changes/bug18716
@@ -0,0 +1,4 @@
+  o Minor bugfixes (assert, portability):
+    - Fix an assertion failure in memarea.c on systems where "long" is
+      shorter than the size of a pointer.
+      Fixes bug 18716; bugfix on 0.2.1.1-alpha
diff --git a/src/common/memarea.c b/src/common/memarea.c
index cfba80be93..0a3fd009b0 100644
--- a/src/common/memarea.c
+++ b/src/common/memarea.c
@@ -24,9 +24,9 @@
 /** A value which, when masked out of a pointer, produces a maximally aligned
  * pointer. */
 #if MEMAREA_ALIGN == 4
-#define MEMAREA_ALIGN_MASK 3lu
+#define MEMAREA_ALIGN_MASK ((uintptr_t)3)
 #elif MEMAREA_ALIGN == 8
-#define MEMAREA_ALIGN_MASK 7lu
+#define MEMAREA_ALIGN_MASK ((uintptr_t)7)
 #else
 #error "void* is neither 4 nor 8 bytes long. I don't know how to align stuff."
 #endif