diff --git a/scripts/mk_genfile_common.py b/scripts/mk_genfile_common.py
index 51d68f56c..cbeb8a82d 100644
--- a/scripts/mk_genfile_common.py
+++ b/scripts/mk_genfile_common.py
@@ -323,6 +323,9 @@ def mk_z3consts_java_internal(api_files, package_name, output_dir):
                         generated_enumeration_files.append(efile.name)
                         efile.write('/**\n *  Automatically generated file\n **/\n\n')
                         efile.write('package %s.enumerations;\n\n' % package_name)
+                        efile.write('import java.util.HashMap;\n')
+                        efile.write('import java.util.Map;\n')
+                        efile.write('\n')
 
                         efile.write('/**\n')
                         efile.write(' * %s\n' % name)
@@ -342,9 +345,18 @@ def mk_z3consts_java_internal(api_files, package_name, output_dir):
                         efile.write('    %s(int v) {\n' % name)
                         efile.write('        this.intValue = v;\n')
                         efile.write('    }\n\n')
+                        efile.write('    // Cannot initialize map in constructor, so need to do it lazily.\n')
+                        efile.write('    // Easiest thread-safe way is the initialization-on-demand holder pattern.\n')
+                        efile.write('    private static class %s_MappingHolder {\n' % name)
+                        efile.write('        private static final Map<Integer, %s> intMapping = new HashMap<>();\n' % name)
+                        efile.write('        static {\n')
+                        efile.write('            for (%s k : %s.values())\n' % (name, name))
+                        efile.write('                intMapping.put(k.toInt(), k);\n')
+                        efile.write('        }\n')
+                        efile.write('    }\n\n')
                         efile.write('    public static final %s fromInt(int v) {\n' % name)
-                        efile.write('        for (%s k: values()) \n' % name)
-                        efile.write('            if (k.intValue == v) return k;\n')
+                        efile.write('        %s k = %s_MappingHolder.intMapping.get(v);\n' % (name, name))
+                        efile.write('        if (k != null) return k;\n')
                         efile.write('        throw new IllegalArgumentException("Illegal value " + v + " for %s");\n' % name)
                         efile.write('    }\n\n')
                         efile.write('    public final int toInt() { return this.intValue; }\n')