diff --git a/cmd/tools/fast/fast.v b/cmd/tools/fast/fast.v
index 822a2b1155..abbc472e6b 100644
--- a/cmd/tools/fast/fast.v
+++ b/cmd/tools/fast/fast.v
@@ -42,10 +42,10 @@ fn main() {
 		return
 	}
 	*/
-	last_commits := exec('git log --pretty=format:"%h" -n 20').split('\n')
+	last_commits := exec('git log --pretty=format:"%h" -n 50').split('\n')
 	// Fetch all unprocessed commits (commits after the last processed commit)
 	mut commits := []string{}
-	println('last_commit="$commit_hash"')
+	println('!last_commit="$commit_hash"')
 	for i, c in last_commits {
 		if c == commit_hash {
 			commits = last_commits[..i].reverse()
diff --git a/vlib/strings/builder_test.v b/vlib/strings/builder_test.v
index 490cf21679..83f64c891d 100644
--- a/vlib/strings/builder_test.v
+++ b/vlib/strings/builder_test.v
@@ -1,5 +1,7 @@
 import strings
 
+type MyInt = int
+
 fn test_sb() {
 	mut sb := strings.Builder{}
 	sb.write('hi')
@@ -15,7 +17,20 @@ fn test_sb() {
 	sb.write('b')
 	assert sb.len == 2
 	assert sb.str() == 'ab'
-	///
+	// Test interpolation optimization
+	sb = strings.new_builder(10)
+	x := 10
+	y := MyInt(20)
+	sb.writeln('x = $x y = $y')
+	res := sb.str()
+	assert res[res.len-1] == `\n`
+	println('"$res"')
+	assert res.trim_space() == 'x = 10 y = 20'
+	//
+	sb = strings.new_builder(10)
+	sb.write('x = $x y = $y')
+	assert sb.str() == 'x = 10 y = 20'
+
 	$if !windows {
 		// TODO msvc bug
 		sb = strings.new_builder(10)
diff --git a/vlib/v/gen/str.v b/vlib/v/gen/str.v
index 93b81906b9..59967e2763 100644
--- a/vlib/v/gen/str.v
+++ b/vlib/v/gen/str.v
@@ -146,22 +146,15 @@ fn (mut g Gen) string_inter_literal_sb_optimized(call_expr ast.CallExpr) {
 	// sb_name := g.cur_call_expr.left
 	// g.go_before_stmt(0)
 	g.writeln('// sb inter opt')
-	write := 'writeln'
-	/*
-	if node.vals.len != node.exprs.len {
-		println('NOPE')
-		println(node.vals)
-		println('==========')
-		println(node.exprs)
-	}
-	*/
+	is_nl := call_expr.name == 'writeln'
+	// println('optimize sb $call_expr.name')
 	for i, val in node.vals {
 		escaped_val := val.replace_each(['"', '\\"', '\r\n', '\\n', '\n', '\\n', '%', '%%'])
 		// if val == '' {
 		// break
 		// continue
 		// }
-		g.write('strings__Builder_${write}(&')
+		g.write('strings__Builder_write(&')
 		g.expr(call_expr.left)
 		g.write(', tos_lit("')
 		g.write(escaped_val)
@@ -173,11 +166,23 @@ fn (mut g Gen) string_inter_literal_sb_optimized(call_expr ast.CallExpr) {
 		// if node.expr_types.len <= i || node.exprs.len <= i {
 		// continue
 		// }
-		g.write('strings__Builder_${write}(&')
+		if is_nl && i == node.exprs.len - 1 {
+			g.write('strings__Builder_writeln(&')
+		} else {
+			g.write('strings__Builder_write(&')
+		}
 		g.expr(call_expr.left)
 		g.write(', ')
-		g.write(g.typ(node.expr_types[i]))
-		g.write('_str(')
+		typ := node.expr_types[i]
+		sym := g.table.get_type_symbol(typ)
+		// if typ.is_number() {
+		if sym.kind == .alias && (sym.info as table.Alias).parent_type.is_number() {
+			// Handle number aliases TODO this must be more generic, handled by g.typ()?
+			g.write('int_str(')
+		} else {
+			g.write(g.typ(typ))
+			g.write('_str(')
+		}
 		g.expr(node.exprs[i])
 		g.writeln('));')
 	}