diff --git a/tools/emul/shell/shell.c b/tools/emul/shell/shell.c
index 4dc4717..d24e565 100644
--- a/tools/emul/shell/shell.c
+++ b/tools/emul/shell/shell.c
@@ -41,7 +41,6 @@
 #define FS_ADDR_PORT 0x02
 
 static uint8_t fsdev[MAX_FSDEV_SIZE] = {0};
-static uint32_t fsdev_size = 0;
 static uint32_t fsdev_ptr = 0;
 // 0 = idle, 1 = received MSB (of 24bit addr), 2 = received middle addr
 static int  fsdev_addr_lvl = 0;
@@ -62,16 +61,13 @@ static uint8_t iord_fsdata()
         fprintf(stderr, "Reading FSDEV in the middle of an addr op (%d)\n", fsdev_ptr);
         return 0;
     }
-    if (fsdev_ptr < fsdev_size) {
+    if (fsdev_ptr < MAX_FSDEV_SIZE) {
 #ifdef DEBUG
         fprintf(stderr, "Reading FSDEV at offset %d\n", fsdev_ptr);
 #endif
         return fsdev[fsdev_ptr];
     } else {
-        // don't warn when ==, we're not out of bounds, just at the edge.
-        if (fsdev_ptr > fsdev_size) {
-            fprintf(stderr, "Out of bounds FSDEV read at %d\n", fsdev_ptr);
-        }
+        fprintf(stderr, "Out of bounds FSDEV read at %d\n", fsdev_ptr);
         return 0;
     }
 }
@@ -80,11 +76,9 @@ static uint8_t iord_fsaddr()
 {
     if (fsdev_addr_lvl != 0) {
         return 3;
-    } else if (fsdev_ptr > fsdev_size) {
-        fprintf(stderr, "Out of bounds FSDEV addr request at %d / %d\n", fsdev_ptr, fsdev_size);
+    } else if (fsdev_ptr >= MAX_FSDEV_SIZE) {
+        fprintf(stderr, "Out of bounds FSDEV addr request at %d / %d\n", fsdev_ptr, MAX_FSDEV_SIZE);
         return 2;
-    } else if (fsdev_ptr == fsdev_size) {
-        return 1;
     } else {
         return 0;
     }
@@ -105,18 +99,11 @@ static void iowr_fsdata(uint8_t val)
         fprintf(stderr, "Writing to FSDEV in the middle of an addr op (%d)\n", fsdev_ptr);
         return;
     }
-    if (fsdev_ptr < fsdev_size) {
+    if (fsdev_ptr < MAX_FSDEV_SIZE) {
 #ifdef DEBUG
         fprintf(stderr, "Writing to FSDEV (%d)\n", fsdev_ptr);
 #endif
         fsdev[fsdev_ptr] = val;
-    } else if ((fsdev_ptr == fsdev_size) && (fsdev_ptr < MAX_FSDEV_SIZE)) {
-        // We're at the end of fsdev, grow it
-        fsdev[fsdev_ptr] = val;
-        fsdev_size++;
-#ifdef DEBUG
-        fprintf(stderr, "Growing FSDEV (%d)\n", fsdev_ptr);
-#endif
     } else {
         fprintf(stderr, "Out of bounds FSDEV write at %d\n", fsdev_ptr);
     }
@@ -167,13 +154,14 @@ int main(int argc, char *argv[])
     if (fp != NULL) {
         fprintf(stderr, "Initializing filesystem\n");
         int i = 0;
-        int c = fgetc(fp);
-        while (c != EOF) {
-            fsdev[i] = c & 0xff;
-            i++;
-            c = fgetc(fp);
+        int c;
+        while ((c = fgetc(fp)) != EOF && i < MAX_FSDEV_SIZE) {
+            fsdev[i++] = c & 0xff;
+        }
+        if (i == MAX_FSDEV_SIZE) {
+            fprintf(stderr, "Filesytem image too large.\n");
+            return 1;
         }
-        fsdev_size = i;
         pclose(fp);
     }