diff --git a/tests/js/numeric-separators/__snapshots__/jsfmt.spec.js.snap b/tests/js/numeric-separators/__snapshots__/jsfmt.spec.js.snap
new file mode 100644
index 000000000000..76095c788dd9
--- /dev/null
+++ b/tests/js/numeric-separators/__snapshots__/jsfmt.spec.js.snap
@@ -0,0 +1,21 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`number.js format 1`] = `
+====================================options=====================================
+parsers: ["babel", "typescript"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+// https://github.com/babel/babel/pull/11854
+
+a = 09e1_1;
+a = 09.1_1;
+
+=====================================output=====================================
+// https://github.com/babel/babel/pull/11854
+
+a = 09e1_1;
+a = 09.1_1;
+
+================================================================================
+`;
diff --git a/tests/js/numeric-separators/jsfmt.spec.js b/tests/js/numeric-separators/jsfmt.spec.js
new file mode 100644
index 000000000000..858ac91aadcc
--- /dev/null
+++ b/tests/js/numeric-separators/jsfmt.spec.js
@@ -0,0 +1 @@
+run_spec(__dirname, ["babel", "typescript"]);
diff --git a/tests/js/numeric-separators/number.js b/tests/js/numeric-separators/number.js
new file mode 100644
index 000000000000..2edc84a44dcb
--- /dev/null
+++ b/tests/js/numeric-separators/number.js
@@ -0,0 +1,4 @@
+// https://github.com/babel/babel/pull/11854
+
+a = 09e1_1;
+a = 09.1_1;
diff --git a/tests/misc/errors/flow/__snapshots__/jsfmt.spec.js.snap b/tests/misc/errors/flow/__snapshots__/jsfmt.spec.js.snap
index ad9d3156c6aa..fcb3de7fa45b 100644
--- a/tests/misc/errors/flow/__snapshots__/jsfmt.spec.js.snap
+++ b/tests/misc/errors/flow/__snapshots__/jsfmt.spec.js.snap
@@ -27,3 +27,12 @@ exports[`module-attributes-static.js error test 1`] = `
     |                            ^^^^
   2 | "
 `;
+
+exports[`number.js error test 1`] = `
+"Unexpected token ILLEGAL (3:5)
+  1 | // https://github.com/babel/babel/pull/11854
+  2 | 
+> 3 | a = 09e1_1;
+    |     ^^^^
+  4 | "
+`;
diff --git a/tests/misc/errors/flow/number.js b/tests/misc/errors/flow/number.js
new file mode 100644
index 000000000000..df9aa2183371
--- /dev/null
+++ b/tests/misc/errors/flow/number.js
@@ -0,0 +1,3 @@
+// https://github.com/babel/babel/pull/11854
+
+a = 09e1_1;