diff --git a/linux-user/main.c b/linux-user/main.c
index aa95db3a6d..23ad357b50 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -48,8 +48,19 @@ unsigned long mmap_min_addr;
 #if defined(CONFIG_USE_GUEST_BASE)
 unsigned long guest_base;
 int have_guest_base;
+#if (TARGET_LONG_BITS == 32) && (HOST_LONG_BITS == 64)
+/*
+ * When running 32-on-64 we should make sure we can fit all of the possible
+ * guest address space into a contiguous chunk of virtual host memory.
+ *
+ * This way we will never overlap with our own libraries or binaries or stack
+ * or anything else that QEMU maps.
+ */
+unsigned long reserved_va = 0xf7000000;
+#else
 unsigned long reserved_va;
 #endif
+#endif
 
 static void usage(void);