diff --git a/block-cache/io_engine.h b/block-cache/io_engine.h
index 1704251..0e13957 100644
--- a/block-cache/io_engine.h
+++ b/block-cache/io_engine.h
@@ -10,13 +10,17 @@
 #include <libaio.h>
 #include <vector>
 
+#include <limits.h>
+#ifndef PAGE_SIZE
+#define PAGE_SIZE sysconf(_SC_PAGE_SIZE)
+#endif
+
 //----------------------------------------------------------------
 
 namespace bcache {
 	using sector_t = uint64_t;
 
 	unsigned const SECTOR_SHIFT = 9;
-	unsigned const PAGE_SIZE = 4096;
 
 	// Virtual base class to aid unit testing
 	class io_engine {
diff --git a/unit-tests/io_engine_t.cc b/unit-tests/io_engine_t.cc
index 2790eb6..d9a25e3 100644
--- a/unit-tests/io_engine_t.cc
+++ b/unit-tests/io_engine_t.cc
@@ -23,6 +23,10 @@
 
 
 #include <fcntl.h>
+#include <limits.h>
+#ifndef PAGE_SIZE
+#define PAGE_SIZE sysconf(_SC_PAGE_SIZE)
+#endif
 
 using namespace boost;
 using namespace std;
@@ -33,7 +37,6 @@ using namespace testing;
 
 namespace {
 	unsigned const MAX_IO = 64;
-	unsigned const PAGE_SIZE = 4096;
 
 	class IOEngineTests : public Test {
 	public: