diff --git a/memory/selector.c b/memory/selector.c
index 86c50e8..6cab776 100644
--- a/memory/selector.c
+++ b/memory/selector.c
@@ -442,8 +442,8 @@
     if (IS_SELECTOR_FREE(sel)) return TRUE;
     LDT_GetEntry( SELECTOR_TO_ENTRY(sel), &entry );
     if ((entry.type == SEGMENT_CODE) && entry.read_only) return TRUE;
-    if (strlen(PTR_SEG_TO_LIN(ptr)) < size) size = strlen(PTR_SEG_TO_LIN(ptr));
-    if (OFFSETOF(ptr) + size - 1 > GET_SEL_LIMIT(sel)) return TRUE;
+    if (strlen(PTR_SEG_TO_LIN(ptr)) < size) size = strlen(PTR_SEG_TO_LIN(ptr)) + 1;
+    if (size && (OFFSETOF(ptr) + size - 1 > GET_SEL_LIMIT(sel))) return TRUE;
     return FALSE;
 }
 
@@ -461,7 +461,7 @@
     if (IS_SELECTOR_FREE(sel)) return TRUE;
     LDT_GetEntry( SELECTOR_TO_ENTRY(sel), &entry );
     if ((entry.type == SEGMENT_CODE) && entry.read_only) return TRUE;
-    if (OFFSETOF(ptr) + size - 1 > GET_SEL_LIMIT(sel)) return TRUE;
+    if (size && (OFFSETOF(ptr) + size - 1 > GET_SEL_LIMIT(sel))) return TRUE;
     return FALSE;
 }
 
@@ -479,7 +479,7 @@
     if (IS_SELECTOR_FREE(sel)) return TRUE;
     LDT_GetEntry( SELECTOR_TO_ENTRY(sel), &entry );
     if ((entry.type == SEGMENT_CODE) || entry.read_only) return TRUE;
-    if (OFFSETOF(ptr) + size - 1 > GET_SEL_LIMIT(sel)) return TRUE;
+    if (size && (OFFSETOF(ptr) + size - 1 > GET_SEL_LIMIT(sel))) return TRUE;
     return FALSE;
 }