diff --git a/regress/deadlock_1.py b/regress/deadlock_1.py
new file mode 100755
index 00000000..702376a3
--- /dev/null
+++ b/regress/deadlock_1.py
@@ -0,0 +1,11 @@
+#!/usr/bin/python
+# From issue #1 of Ryan Hileman
+
+from unicorn import *
+
+CODE = b"\x90\x91\x92"
+
+mu = Uc(UC_ARCH_X86, UC_MODE_64)
+mu.mem_map(0x100000, 4 * 1024)
+mu.mem_write(0x100000, CODE)
+mu.emu_start(0x100000, 0x1000 + len(CODE))
diff --git a/uc.c b/uc.c
index c9043750..3c59f0c8 100644
--- a/uc.c
+++ b/uc.c
@@ -554,7 +554,7 @@ uc_err uc_mem_map(uch handle, uint64_t address, size_t size)
 
     // align to 8KB boundary
     map_begin[map_count] = address & (~ (8*1024 - 1));
-    s = (size + 8*1024 - 1) & (~ (8*1024));
+    s = (size + 8*1024 - 1) & (~ (8*1024 - 1));
     map_end[map_count] = s + map_begin[map_count];
     uc->memory_map(uc, map_begin[map_count], s);
     map_count++;