diff --git a/nasmlib.c b/nasmlib.c
index e380542d..64d85b91 100644
--- a/nasmlib.c
+++ b/nasmlib.c
@@ -1088,6 +1088,22 @@ int bsi(char *string, const char **array, int size)
     return -1;                  /* we haven't got it :( */
 }
 
+int bsii(char *string, const char **array, int size)
+{
+    int i = -1, j = size;       /* always, i < index < j */
+    while (j - i >= 2) {
+        int k = (i + j) / 2;
+        int l = nasm_stricmp(string, array[k]);
+        if (l < 0)              /* it's in the first half */
+            j = k;
+        else if (l > 0)         /* it's in the second half */
+            i = k;
+        else                    /* we've got it :) */
+            return k;
+    }
+    return -1;                  /* we haven't got it :( */
+}
+
 static char *file_name = NULL;
 static int32_t line_number = 0;
 
diff --git a/nasmlib.h b/nasmlib.h
index 4bfec686..70da2146 100644
--- a/nasmlib.h
+++ b/nasmlib.h
@@ -257,8 +257,11 @@ int32_t reloc_wrt(expr *);
  * Binary search routine. Returns index into `array' of an entry
  * matching `string', or <0 if no match. `array' is taken to
  * contain `size' elements.
+ *
+ * bsi() is case sensitive, bsii() is case insensitive.
  */
 int bsi(char *string, const char **array, int size);
+int bsii(char *string, const char **array, int size);
 
 char *src_set_fname(char *newname);
 int32_t src_set_linnum(int32_t newline);