diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index c743b5e25b..627ea17918 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -10,6 +10,7 @@ import v.pref
 import v.token
 import v.util
 import v.depgraph
+import os
 
 // NB: keywords after 'new' are reserved in C++
 const (
@@ -2762,8 +2763,9 @@ fn (mut g Gen) write_init_function() {
 	}
 	if g.pref.autofree {
 		// Pre-allocate the string buffer
-		// TODO make it configurable
-		g.writeln('g_str_buf = malloc(1024 * 1000);')
+		s_str_buf_size := os.getenv('V_STRBUF_MB')
+		mb_size := if s_str_buf_size == '' { 1 } else { s_str_buf_size.int() }
+		g.writeln('g_str_buf = malloc( ${mb_size} * 1024 * 1000 );')
 	}
 	g.writeln('\tbuiltin_init();')
 	g.writeln('\tvinit_string_literals();')
@@ -2785,6 +2787,7 @@ fn (mut g Gen) write_init_function() {
 		g.writeln('void _vcleanup() {')
 		// g.writeln('puts("cleaning up...");')
 		g.writeln(g.cleanups.str())
+		g.writeln('\tfree(g_str_buf);')
 		g.writeln('}')
 		if g.pref.printfn_list.len > 0 && '_vcleanup' in g.pref.printfn_list {
 			println(g.out.after(fn_vcleanup_start_pos))