diff --git a/csi.c b/csi.c
index 558c2dc2..494ac957 100644
--- a/csi.c
+++ b/csi.c
@@ -1924,26 +1924,27 @@ csi_dispatch(struct terminal *term, uint8_t final)
         }
 
         case 'x': {  /* DECFRA */
-            const char c = vt_param_get(term, 0, 0);
-            if (likely((c >= 32 && c < 126) ||
-                       (c >= 160 && c <= 255)))
+            const uint8_t c = vt_param_get(term, 0, 0);
+
+            if (unlikely(!((c >= 32 && c < 126) || c >= 160)))
+                break;
+
+            int top, left, bottom, right;
+            if (!params_to_rectangular_area(
+                    term, 1, &top, &left, &bottom, &right))
             {
-                int top, left, bottom, right;
-                if (!params_to_rectangular_area(
-                        term, 1, &top, &left, &bottom, &right))
-                {
-                    break;
-                }
-
-                /* Erase the entire region at once (MUCH cheaper than
-                 * doing it row by row, or even character by
-                 * character). */
-                sixel_overwrite_by_rectangle(
-                    term, top, left, bottom - top + 1, right - left + 1);
-
-                for (int r = top; r <= bottom; r++)
-                    term_fill(term, r, left, c, right - left + 1, true);
+                break;
             }
+
+            /* Erase the entire region at once (MUCH cheaper than
+             * doing it row by row, or even character by
+             * character). */
+            sixel_overwrite_by_rectangle(
+                term, top, left, bottom - top + 1, right - left + 1);
+
+            for (int r = top; r <= bottom; r++)
+                term_fill(term, r, left, c, right - left + 1, true);
+
             break;
         }
 
diff --git a/terminal.c b/terminal.c
index acde951b..1ca581be 100644
--- a/terminal.c
+++ b/terminal.c
@@ -3511,7 +3511,7 @@ print_spacer(struct terminal *term, int col, int remaining)
  *   - double width characters not supported
  */
 void
-term_fill(struct terminal *term, int r, int c, char data, size_t count,
+term_fill(struct terminal *term, int r, int c, uint8_t data, size_t count,
     bool use_sgr_attrs)
 {
     struct row *row = grid_row(term->grid, r);
diff --git a/terminal.h b/terminal.h
index c8a43c64..0dd40c51 100644
--- a/terminal.h
+++ b/terminal.h
@@ -798,7 +798,7 @@ void term_cursor_down(struct terminal *term, int count);
 void term_cursor_blink_update(struct terminal *term);
 
 void term_print(struct terminal *term, char32_t wc, int width);
-void term_fill(struct terminal *term, int row, int col, char c, size_t count,
+void term_fill(struct terminal *term, int row, int col, uint8_t c, size_t count,
                bool use_sgr_attrs);
 
 void term_scroll(struct terminal *term, int rows);