diff --git a/src/main/scala/leon/codegen/CodeGeneration.scala b/src/main/scala/leon/codegen/CodeGeneration.scala
index 7f20b7195fbd670aeeff28c706aba16b296864ed..dc674dfbf2e7f35ba89fe2fbe6bc402d63e1bbde 100644
--- a/src/main/scala/leon/codegen/CodeGeneration.scala
+++ b/src/main/scala/leon/codegen/CodeGeneration.scala
@@ -1182,7 +1182,7 @@ trait CodeGeneration {
         ch << InvokeStatic(StrOpsClass, "intToString", s"(I)L$JavaStringClass;")
       case BooleanToString(a) =>
         mkExpr(a, ch)
-        ch << InvokeStatic(StrOpsClass, "booleanToString", s"(z)L$JavaStringClass;")
+        ch << InvokeStatic(StrOpsClass, "booleanToString", s"(Z)L$JavaStringClass;")
       case IntegerToString(a) =>
         mkExpr(a, ch)
         ch << InvokeStatic(StrOpsClass, "bigIntToString", s"(L$BigIntClass;)L$JavaStringClass;")