diff --git a/emu/memory.c b/emu/memory.c
index 67782c4bbf..593835dd51 100644
--- a/emu/memory.c
+++ b/emu/memory.c
@@ -115,8 +115,15 @@ int pt_set_flags(struct mem *mem, page_t start, pages_t pages, int flags) {
     for (page_t page = start; page < start + pages; page++)
         if (mem->pt[page].data == NULL)
             return _ENOMEM;
-    for (page_t page = start; page < start + pages; page++)
-        mem->pt[page].flags = flags;
+    for (page_t page = start; page < start + pages; page++) {
+        struct pt_entry *entry = &mem->pt[page];
+        entry->flags = flags;
+        void *data = (char *) entry->data->data + entry->offset;
+        int prot = PROT_READ;
+        if (flags & P_WRITE) prot |= PROT_WRITE;
+        if (mprotect(data, PAGE_SIZE, prot) < 0)
+            return errno_map();
+    }
     mem_changed(mem);
     return 0;
 }
diff --git a/fs/real.c b/fs/real.c
index 041c702fab..dca00be9b4 100644
--- a/fs/real.c
+++ b/fs/real.c
@@ -152,13 +152,17 @@ off_t realfs_lseek(struct fd *fd, off_t offset, int whence) {
 int realfs_mmap(struct fd *fd, struct mem *mem, page_t start, pages_t pages, off_t offset, int prot, int flags) {
     if (pages == 0)
         return 0;
+
     int mmap_flags = 0;
     if (flags & MMAP_PRIVATE) mmap_flags |= MAP_PRIVATE;
     if (flags & MMAP_SHARED) mmap_flags |= MAP_SHARED;
+    int mmap_prot = PROT_READ;
+    if (prot & P_WRITE) mmap_prot |= PROT_WRITE;
+
     off_t real_offset = (offset / real_page_size) * real_page_size;
     off_t correction = offset - real_offset;
     char *memory = mmap(NULL, (pages * PAGE_SIZE) + correction,
-            PROT_READ | PROT_WRITE, mmap_flags, fd->real_fd, real_offset);
+            mmap_prot, mmap_flags, fd->real_fd, real_offset);
     if (memory != MAP_FAILED)
         memory += correction;
     return pt_map(mem, start, pages, memory, prot);
diff --git a/kernel/exec.c b/kernel/exec.c
index fdc4af0ae7..05d6a0cc60 100644
--- a/kernel/exec.c
+++ b/kernel/exec.c
@@ -67,7 +67,7 @@ static int load_entry(struct prg_header ph, addr_t bias, struct fd *fd) {
     addr_t memsize = ph.memsize;
     addr_t filesize = ph.filesize;
 
-    int flags = 0;
+    int flags = P_READ;
     if (ph.flags & PH_W) flags |= P_WRITE;
 
     if ((err = fd->ops->mmap(fd, curmem, PAGE(addr),