diff --git a/lib/md037.js b/lib/md037.js
index 95cd2c31..2a74b471 100644
--- a/lib/md037.js
+++ b/lib/md037.js
@@ -4,8 +4,8 @@
 
 const { addErrorContext, forEachInlineChild } = require("../helpers");
 
-const leftSpaceRe = /(?:^|\s)(\*\*?|__?)\s.*[^\\]\1/g;
-const rightSpaceRe = /(?:^|[^\\])(\*\*?|__?).+\s\1(?:\s|$)/g;
+const leftSpaceRe = /(?:^|\s)(\*\*?\*?|__?_?)\s.*[^\\]\1/g;
+const rightSpaceRe = /(?:^|[^\\])(\*\*?\*?|__?_?).+\s\1(?:\s|$)/g;
 
 module.exports = {
   "names": [ "MD037", "no-space-in-emphasis" ],
diff --git a/test/spaces_inside_emphasis_markers.md b/test/spaces_inside_emphasis_markers.md
index 7dceb24b..6d8aee82 100644
--- a/test/spaces_inside_emphasis_markers.md
+++ b/test/spaces_inside_emphasis_markers.md
@@ -4,26 +4,38 @@ Line with *Normal emphasis*
 
 Line with **Normal strong**
 
+Line with ***Normal strong and emphasis***
+
 Line with _Normal emphasis_
 
 Line with __Normal strong__
 
+Line with ___Normal strong and emphasis___
+
 Broken * emphasis * with spaces in {MD037}
 
 Broken ** strong ** with spaces in {MD037}
 
+Broken *** strong and emphasis *** with spaces in {MD037}
+
 Broken _ emphasis _ with spaces in {MD037}
 
 Broken __ strong __ with spaces in {MD037}
 
+Broken ___ strong and emphasis ___ with spaces in {MD037}
+
 Mixed *ok emphasis* and * broken emphasis * {MD037}
 
 Mixed **ok strong** and ** broken strong ** {MD037}
 
+Mixed ***ok strong and emphasis*** and *** broken strong and emphasis *** {MD037}
+
 Mixed _ok emphasis_ and _ broken emphasis _ {MD037}
 
 Mixed __ok strong__ and __ broken strong __ {MD037}
 
+Mixed ___ok strong and emphasis___ and ___ broken strong and emphasis ___ {MD037}
+
 Mixed *ok emphasis* **ok strong** * broken emphasis * {MD037}
 
 Multiple * broken emphasis * _ broken emphasis _ {MD037}
@@ -40,30 +52,46 @@ The same goes for words* with asterisks* after them.
 
 ** Strong** with left space {MD037}
 
+*** Strong and emphasis*** with left space {MD037}
+
 _ Emphasis_ with left space {MD037}
 
 __ Strong__ with left space {MD037}
 
+___ Strong and emphasis___ with left space {MD037}
+
 *Emphasis * with right space {MD037}
 
 **Strong ** with right space {MD037}
 
+***Strong and emphasis *** with right space {MD037}
+
 _Emphasis _ with right space {MD037}
 
 __Strong __ with right space {MD037}
 
+___Strong and emphasis ___ with right space {MD037}
+
 {MD037} Left space * emphasis*
 
 {MD037} Left space ** strong**
 
+{MD037} Left space *** strong and emphasis***
+
 {MD037} Left space _ emphasis_
 
 {MD037} Left space __ strong__
 
+{MD037} Left space ___ strong and emphasis___
+
 {MD037} Right space *emphasis *
 
 {MD037} Right space **strong **
 
+{MD037} Right space ***strong and emphasis ***
+
 {MD037} Right space _emphasis _
 
 {MD037} Right space __strong __
+
+{MD037} Right space ___strong and emphasis ___