diff --git a/library/constant_time.c b/library/constant_time.c
index c823b78..6e02f34 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -78,8 +78,10 @@
     uint32_t r;
 #if defined(__arm__) || defined(__thumb__) || defined(__thumb2__)
     asm volatile ("ldr %0, [%1]" : "=r" (r) : "r" (p) :);
-#elif defined(__aarch64__)
+#elif defined(__aarch64__) && (SIZE_MAX == 0xffffffffffffffff)
     asm volatile ("ldr %w0, [%1]" : "=r" (r) : "r" (p) :);
+#elif defined(__aarch64__) && (SIZE_MAX == 0xffffffff)
+    asm volatile ("ldr %w0, [%w1]" : "=r" (r) : "r" (p) :);
 #endif
     return r;
 }