diff --git a/ansi2html.h b/ansi2html.h
index 21a1c09..6478c28 100644
--- a/ansi2html.h
+++ b/ansi2html.h
@@ -82,7 +82,7 @@ static int color_css(char* buf, size_t size, int32_t color, int is_bg) {
 }
 
 static char* vterm_render(const vterm_t* vt) {
-    const size_t cap =
+    const size_t cap = 1024
          + (size_t)(vt->last_row + 1) * 4
          + (size_t)(vt->last_row + 1) * (vt->last_col + 1) *
              (sizeof("<span class=\" b i u s d k\" style=\"color:#xxxxxx;background:#xxxxxx;\">&amp;</span>") - 1);
@@ -288,13 +288,14 @@ static int utf8_len(const unsigned char c) {
 }
 
 static char* ansi2html(const char* ansislop) {
-    vterm_t vt = {0};
+    vterm_t* vt = malloc(sizeof(vterm_t));
+    memset(vt, 0, sizeof(vterm_t));
 
-    vt.slop.fg = vt.slop.bg = -1;
+    vt->slop.fg = vt->slop.bg = -1;
     for (int r = 0; r < VTERM_ROWS; r++) {
         for (int c = 0; c < VTERM_COLS; c++) {
-            vt.cells[r][c].slop.fg = vt.cells[r][c].slop.bg = -1;
-            vt.cells[r][c].utf8[0] = ' ';
+            vt->cells[r][c].slop.fg = vt->cells[r][c].slop.bg = -1;
+            vt->cells[r][c].utf8[0] = ' ';
         }
     }
 
@@ -302,7 +303,7 @@ static char* ansi2html(const char* ansislop) {
         if (*p == '\e') {
             p++;
             if (*p == '[') {
-                p = vterm_csi(&vt, p + 1);
+                p = vterm_csi(vt, p + 1);
             }
             else if (*p == '(') {
                 p += 2;
@@ -313,19 +314,19 @@ static char* ansi2html(const char* ansislop) {
         }
         else if (*p == '\r') {
             p++;
-            vt.col = 0;
+            vt->col = 0;
         }
         else if (*p == '\n') {
             p++;
-            vt.col = 0;
-            vt.row++;
+            vt->col = 0;
+            vt->row++;
         }
         else if (*p == '\t') {
             p++;
-            vt.col = (vt.col + 8) & ~7;
-            if (vt.col >= VTERM_COLS) {
-                vt.col = 0;
-                vt.row++;
+            vt->col = (vt->col + 8) & ~7;
+            if (vt->col >= VTERM_COLS) {
+                vt->col = 0;
+                vt->row++;
             }
         }
         else if ((uint8_t)*p < 0x20) {
@@ -333,9 +334,11 @@ static char* ansi2html(const char* ansislop) {
         }
         else {
             const int l = utf8_len((unsigned char)*p);
-            vterm_put(&vt, p, l);
+            vterm_put(vt, p, l);
             p += l;
         }
     }
-    return vterm_render(&vt);
+    char* html = vterm_render(vt);
+    free(vt);
+    return html;
 }