diff --git a/arch/um/sys-i386/unmap.c b/arch/um/sys-i386/unmap.c
index 136875263d2..1b0ad0e4adc 100644
--- a/arch/um/sys-i386/unmap.c
+++ b/arch/um/sys-i386/unmap.c
@@ -15,7 +15,7 @@ int switcheroo(int fd, int prot, void *from, void *to, int size)
 	if(munmap(to, size) < 0){
 		return(-1);
 	}
-	if(mmap2(to, size, prot, MAP_SHARED | MAP_FIXED, fd, 0) != to){
+	if(mmap2(to, size, prot, MAP_SHARED | MAP_FIXED, fd, 0) == (void*) -1 ){
 		return(-1);
 	}
 	if(munmap(from, size) < 0){
diff --git a/arch/um/sys-x86_64/unmap.c b/arch/um/sys-x86_64/unmap.c
index bc7094cce47..f4a4bffd8a1 100644
--- a/arch/um/sys-x86_64/unmap.c
+++ b/arch/um/sys-x86_64/unmap.c
@@ -15,7 +15,7 @@ int switcheroo(int fd, int prot, void *from, void *to, int size)
 	if(munmap(to, size) < 0){
 		return(-1);
 	}
-	if(mmap(to, size, prot, MAP_SHARED | MAP_FIXED, fd, 0) != to){
+	if(mmap(to, size, prot, MAP_SHARED | MAP_FIXED, fd, 0) == (void*) -1){
 		return(-1);
 	}
 	if(munmap(from, size) < 0){